Start checking your local Halloween super stores in larger US cities. I just found a plastic costume cap gun complete with orage tip. Funny thing, it looks just like a Smith and Wesson, but the top breaks open like a Webley or an earlier Smith to load the caps. A perfect party holster stuffer only avaiable this time of year. Start looking!
I have an Airsoft gun for my own Halloween party, but I won't dare to go out in public with the thing, especially in Los Angeles. I can't find a decent toy gun in any of the costume or toy stores around here. I guess it's not PC to let kids play with toy firearms anymore.