I would think for a bag of that size 30 adults would be a completely reasonable amount. Personally, before I ever ship fish (same general idea) I always fast them at least 2 days and be sure to add just a tad extra Prime (or other ammonia detoxifier). This negates most of the ammonia issues for the time they're expected to be in the bag, though if you wanted to throw in a piece of the ammonia blocking sponge it definitely wouldn't hurt. As far as oxygen goes for that amount of time as long as you have somewhere around 50/50 air to water I wouldn't imagine there'd be any problem! If you wanted to go one step further and bring them in a cooler with an airstone and bag them there there's also that option, though admittedly more work and much heavier.
As for a wholesaler and how to get in touch with them I'll be waiting to see who chimes in because I am up to my eyeballs in fish and could definitely use some advice as well, lol!