If you want them to last a long time, your best bet is to use one of those vacuum sealer machines. Make several small packages, so you'll only have maybe 1-2 months worth "open" at a time. In between feedings, seal it up as best you can with the ziplock/squeeze the air out method. As long as you have a good freezer, they'll last a very long time in a vacuum sealed bag.
It doesn't matter a whole lot if this guy gives you live or frozen when you are getting pinks & fuzzies, as freezing is considered the most humane way to kill them when they are that young anyway, so you could just take live ones home and put them in your freezer. CO2 is used for older ones, but the babies are resistant to CO2 (presumably to keep them from suffocating under their mother).
Another place to look to find feeders is craigslist. Sometime within the past year or 2, at least in this area, I've started seeing a reasonable number of ads for feeders on there.