you can buy formula from a pet store
Do a search on the net there is a bunch of info
I had the same problem happen to me but with mice and couldn't kill the little guys so I got a syringe and fed them from that(without the actual needle on it)
They lived for probably 2 weeks and then both dies in the same day. Must not have been getting something they needed.
When I started to feed them they were only a week old I think not even a fuzzy yet. You have to feed them a bunch of small meals everyday and help them defecate by rubbing their bums with a warm wet cloth or something of sort.
It's not that I'm lazy; it's that I just don't care.