My guinea pig has lice..help?

I have to guinea pigs, and a while ago I noticed a bald patch one of them, and I took it to the vet, and the vet said they had lice and said she needed to give them a series if shots to get rid of the lice, and it cost 300 dollors. I guess it didn't work becuase I just noticed a bald pTch on my other one . Is there another way to get rid of lice, becuase I don't want to pay another 300 dollars for a treatment that doesn't even work.