Following this post, I use freezer bags for mines meat and soup, I always throw them away though. Interested to see if anyone re-uses them. I'd think bacteria overgrowth may be a problem, because they aren't meant to be washed and re-used.
I wash and re-use ONCE. I have a sealed bucket of bleach solution on my sink. After I empty a baggie and wash it out w/ soap and water I put it in the bleach bucket. I empty the bucket every few days and rewash everything. I wash and rinse rinse rinse in super hot water, then hang them in the shower to dry. But I only do that ONCE. After they're used the second time, I rinse them out and throw them away.
Look for a restaurant supply place or a bulk food store. Both will sell deli containers. I use the 6 oz size and just send them through the dishwasher on the top rack. You'll want to size appropriately for the number of ferrets you have of course. 1 container = 1 days food. You also might want to check out these threads:
I've gotten into the habit of portioning meat into the deli containers, and then putting those into a labeled gallon freezer ziplock. This makes it easier for me to keep track of what's in each container, and since the gallon bags don't get dirty I just leave them there for the next time I get more of that protein.