I keep having issues finding accurate focus on my gh5s, the camera's own peaking is just not good and the lack to punch in to focus makes it a very unreliable camera to judge manual focusing. I do have a Zacuto Z-Finder EVF Pro that I traded with one of my camera's a while back but to be honest, I don't like it, I can only magnify in the center of the screen and the peaking is not that good. Most of my shots are in focus but every wedding I come home to see at least one shot that is slightly out of focus while I was sure it wasn't.

I mainly use this camera to cover speaking heads during ceremonies and speeches at the reception and I often shoot from a distance with a 40-150 f2.8 from Olympus. As I find accurate focus critical I"m looking for another small and light monitor, either bright enough to see in direct sunlight or with a loupe like on my Z-finder, it must be able to punch in to focus in all positions on the monitor and the peaking has to be very good. 5 inch is the max size I want to use.

Any suggestions?

The forthcoming Atomos Ninja V looks a good candidate. Although it is also a recorder,, it is still quite compact. Another benefit is it's maximum level of 1000 nits and compatibility with HDR so there's a possibility to use that in difficult lighting conditions.

The Atomos Ninja V would be a good choice. It recently was released so you might need to wait for it to be in stock. I’m confused by the HDR feature. As far as I understand it effects the display but not what’s recorded. I’m guessing since my eng camera doesn’t film in hdr, it’s irrelevant.

Atomos’s screens are very bright, sharp, and have many display aids in addition to being a recorder. The only downside is it’s a little heavier and bulkier than a field monitor. It’s also pricey but so are quality field monitors.

SmallHD Focus.

That ninja v did cross my mind but kinda pricey at around 1300euro (tax incl) with a 1TB ssd included, it doesn't seem to come with a battery but I have plenty of sony batteries.

Will have to wait for some reviews, if it's that good then it might be worth investing in just to get the recording backup as well in a package not much larger then some 5 inch monitors only, like a smallhd.

I hated the Blackmagic Video Assist. The screen has this green tint and pretty limited in feature as an external recorder.
I have the Atomos Shogun Flame and after seeing their AtomHDR its difficult going back. It looks like half the details are missing when comparing ordinary 8 bit screen to 10 bit HDR screen.

The Atomos Ninja V would be a good choice. It recently was released so you might need to wait for it to be in stock. I’m confused by the HDR feature. As far as I understand it effects the display but not what’s recorded. I’m guessing since my eng camera doesn’t film in hdr, it’s irrelevant. ...

Looking back at your post commenting on the lack of HDR recoding, I checked the Atomos pages on the Ninja V where it says this:
"Eliminate your camera’s internal compression and time limits – record up to 4Kp60 10-bit HDR video direct from your camera's sensor over HDMI 2.0."

The spec. section indicates that it can record in many gamuts including HLG, V Log and various S Log versions. It also says that input and output are 10 bit 4:2:2 through HDMI 2.0, - all requisites for HDR recording.
I have a GH5 which will output HDR through its HDMI 2.0 interface when set to record HEVC HLG (recorded only 4:2:0) so I am looking seriously at the Ninja V.

I hated the Blackmagic Video Assist. The screen has this green tint and pretty limited in feature as an external recorder.
I have the Atomos Shogun Flame and after seeing their AtomHDR its difficult going back. It looks like half the details are missing when comparing ordinary 8 bit screen to 10 bit HDR screen.
I believe the Video Assist also has a coolinf fan that can interfere with microphones mounted near to it.

Started using the Liliput A5 recently, very happy with it for its low price, small size, and good quality for its price:

https://youtu.be/GfoB3r6PBug?t=197

Looking back at your post commenting on the lack of HDR recoding, I checked the Atomos pages on the Ninja V where it says this:
"Eliminate your camera’s internal compression and time limits – record up to 4Kp60 10-bit HDR video direct from your camera's sensor over HDMI 2.0."

The spec. section indicates that it can record in many gamuts including HLG, V Log and various S Log versions. It also says that input and output are 10 bit 4:2:2 through HDMI 2.0, - all requisites for HDR recording.
I have a GH5 which will output HDR through its HDMI 2.0 interface when set to record HEVC HLG (recorded only 4:2:0) so I am looking seriously at the Ninja V.
my cameras film in 8 bit 4:2:0, so when I turned on HDR the dynamic range increased when viewed but it didn’t change what was recorded. I assume if i was filming in flat looking log it would allow me to monitor it as if it was color graded.

I have a Video Assist 5" which eats batteries and has a noisy fan when recording so I just use as a monitor. I too am looking at the Atomos V as it will allow me to record UHD 60P HLG. Do not think it will be available till end of September here.