Coma Kitty Needs Help!

This is little Jake. He is a feral street kitten living in a colony near my home in Mallorca Spain. He is just 6 months old, and I found him almost dead in the street. Fearing he had been hit by a car I rushed him to the out of hours vet. Unfortunately he slipped into a coma, which for 24 hours did not look good. The vet advised me that Jake had in fact been POISONED. The poison caused his poor body to fit over and over again until his brain could no longer cope. No one knows how long this poor boy lay out on the cold street, alone and convulsing before I found him. Luckily after lots of meds from the vet he gradually came around, still with lots of twitching resulting in im staying in the vets for some time until they could check for any lasting brain damage. After 4 day, he got the all clear. Dubbed - "The Miracle" cat by the staff, the little scruff ball came home with me for to rest and finish his course of antibiotics. I will then need to make sure he is vaccinated, wormed and homed to a safe and loving household. I already ave 4 rescue cat and a dog in my small home. I was not overly shocked to see the vet bill at 500euros. We really cannot afford to pay it. We already feed and neuter around 20 cats on the street here, as well a our own rescue pets. If anyone can help us I would really appreciate it!! Mallorca has a massive feral cat problem which I do my best to help by catch, neuter and returning. Any extra funds received will go towards this.