Indiesnap mattbox is effective
 

My indiesnap mattbox arrived today and I'm very happy with it. Friendly, personal service and support. A really nice piece of kit, esp. at that price point. Super easy to put on/take off/use, it allows you to use two full size filters, as well as keeping your uv lens protector in place. It also provides great protection from stray light (I ordered the additional side flags with mine) and is aesthetically pleasing too - if you want to impress talent this will do the job. I'm using mine with an XL2 but you can rig it up to almost anything.