Where to get rubber bullet gun ? Europe. Lots and lots of them. There even are some that are made out of steel, so they cand use more powerful amo. Fort 17 is pretty popular, there are a whole bunch of them fort 9,10,14,18 etc. They come in 9mm rubber bullets or they even have .45 which they just developed. There are others steel-made like Grand Power, Tangfolio , but in my opinion if you want rubber, at the moment fort is the best, with good amo of course. When talking rubber, amo makes the biggest difference.
BTW how much is a glock in the US ?