I probably won't set you back any more than the instant film. I am thinking that midgets will be about 25 cents per bulb, perhaps as much as 50 cents if you are unlucky. I have several *large* plastic crates full of flashbulbs, and I think I spent about $200 total for at least 500 bulbs. Ge #5s, #11s, Sylvania #25s, etc. Quite a lot of huge ones as well...larger than a household tungsten bulb.
Unfortunately I got no midget bulbs, or I would give them to you!
But I would post a classified ad if I were you, or look on eBay. That's how I got mine.