I think a person could dig around in their garage junk or the local pawn shop and find a flat piece of hardened steel, then work it over with a grinder and/or cutoff tool to create a small pry bar. I have an old cheap wood chisel, cut the handle off and that would make a pry bar about 3.5" long. I also have a couple of thin wrenches stamped from flat metal, the kind that you get when you buy a cheap power tool or whatever. I think I could cut off one of those and make a nice light pry bar out of it. Actually I've seen small pry bars at places like HomeDepot. If you wanted to carry one of those in your pocket you would probably still need to cut it down a little bit.
All these ideas, I need to do a little experimenting and make one for myself. It seems to me that 5" or 6" would be the shortest that would allow you to get good leverage with your hand, and that length would still be good for pocket carry.