do a google search on "screen printed beer bottles" and variations. i think the minimums will be much higher than 500pcs however and the costs will be much more than you expect. might be easier to have a template made and paint yourself with sprayer and glass paints? or go old skool with a handmade lino cut affixed to a board, ink it up with a roller, then roll your clean bottle across it, ink again and repeat...
a good source would be to talk to a local brewpub that sells their beer from the bar in pre-printed growlers... they are prob not dealing with huge volume and may reveal their sources.