Can you wear small camera bags that attach onto your belt. You know, the small ones just bigger than your fist, and the belt goes through the belt loops on the back (and they zipper).
Or does it actually have to be a fanny pack with 3 prong clip?
Are these the same requirements as The Hulk Roller Coaster?
If it's small (fits only a pocketable or slightly-larger-than-pocketable) camera, and you actually have to remove your belt to take it off, they would probably let you take it.
If it attaches to your belt with carabiner clips, or is tied to your belt, or has a velcro attachment, or something else similar, all bets are off.
If you plan on wearing something attached to your belt on the ride, it might be worth it to try sitting in the test seats outside before you get in line, just to be sure you will be comfortable with the item attached to you during the ride. The ride itself is about 5 minutes, and you get jostled around a lot, you want to be sure the camera does not poke you annoyingly the whole time.
ETA: Don't know about Hulk, but I wore a small waist bag with a butterbeer mug clipped to it on Dragon Challenge. I started taking it off after that for rides over 50 mph, I was tired of spending the whole ride worrying that it was going to come off and I was going to lose something. I did wear it on Simpsons, MIB, Spiderman, and a few other rides.