Personally I'd go with The Mouse Factory if you're wanting top quality. Phone them and ask for Edna. Explain what you are feeding and she'll help you get the best bang for your buck. If you have concerns about how long any prey item is good to use, the folks that produce f/t prey items are the right people to ask I think.
Their product comes vacuum packed. Once you open the package and remove a few prey items simply put the whole package inside a good ziplock freezer grade storage bag, express the air manually and you're good to go. Either that or simply buy some Glad Press n Seal freezer wrap and wrap the left over prey in that (just leave it in it's original packaging and after expressing any air, wrap it solidly).
I can't see the need for an expensive machine really. If you're concerned about opening a big package every week, then just quickly re-pack the bigger quantities into weekly feeding packages. If you need 2 rat pups and 1 mouse per week then grab the Press n Seal and make your weekly packages up like that.
There is also a product sold at WalMart (sorry I can't remember the name atm) which pumps the air out of a freezer storage bag. My husband says it retails for under $10.00 so I'll have him get me the information on it for you. I think Robin also was telling me about seeing this new product recently.