Suggestions need on a strong directional mini-microphone
 

I am looking for a smaller microphone that is directional, but smaller in size. I would love something like a lapel mic size, but it can be bigger than that. Any suggestions?

I would need it to pick up dialogue for a documentary I am doing where the person isn't informed they are being filmed until after (of course I am getting permission after).

Unidirectional lavs
 

Hi:

The Sony ECM-66B is a uni-directional lavaliere microphone that measures .97 x .44" (24.2 x 10.6mm) and sells for U.S. $350.00

Best,

Dan

so you need a parabolic microphone that you can put far far away the subject.

Any DIY solutions for the parabolic? the sony price tag is a little beyond my budget as well...

Lav mics are designed for close-in micing, 6 to 12 inches from the subject's mouth. Move farther away than that and the voice falls off in a hurry. Those "candid camera" shows you've seen where people are photographed with a hidden camera are setup by enticing the subject into a set that has been plastered with hidden microphones so they're at most a couple of feet from one of them.

Directional mics such as shotguns that can be used farther away than a typical lav are quite a bit larger than a lav would be. A parabolic mic that can give you a standoff distance measured in tens of feet is even larger, a foot to several feet across. Not to mention pricey.

What kind of doco are you doing that the subjects can't know they're being filmed until after the fact? How close can you get the mic to the subject? Even on "Cops" they know they're being filmed as it happens. And you'll notice on shows like "To Catch A Predator" they don't try for much sound until the reveal when the presenter appears on the scene with the soundman in tow. Shows such as "Punked" they mic the location or mic the shill.

I went to a spy shop yesterday and they had one of those whisper 2000-like devices. Does something like that really work?

Sort of. There is no sound quality, it's very thin. The noise suppression system in some of the devices is quite good, but bear in mind they're made for surveilance, not recording the Pops.
If you need to really reach out and grab someone, the AT Array is very well made, and works quite well. And is very spendy.

That is going to be difficult then. I was thinking of just using the on-camera mic, but I am afraid it is going to be problematic at best. I wonder if I put one of those Squid mic and a Iriver under the table if it would pick up a better sound?

if it is around a table there are thousand ways to hide a wireless mic on a table.

What are the details of the setup you need to mic? There may be a way to plant a mic - for example, you said "around a table" ... if it's a cafeteria or bar table, for example, a lav concealed in a salt shaker or napkin dispenser is a common ploy. Another is a boundary microphone hidden in plain sight. There's lots of ways to skin a cat.