Help Mr. Kitty with his amputation

I found Mr. Kitty at a gas station near out shop.  I fed him a can of cat food each day for the weekend until I could catch him and take him to the vet.  I had decided to just drop him off for the local animal program to take care of him.  Only problem is that they were full, wouldn't take him and would just put him down.  So, I decided I would after he so lovingly looked at me and just wanted to be petted.  My husband, when asked what I should do, told me to "Follow my heart".  So, I am.  He will need to have his back leg amputated due to a compound fracture that he has suffered.  This funding is going to go towards his vet bills.  Everything from the blood work, pain meds, ivs and the amputation.  This cat has grown on me so quickly.  He is really sweet, loves attention, just wants to be petted.  I can't let him go now.  Please, help us save him.