RMAC does them for $20 apiece if you let them clip the corner of their ear to denote they are feral and have been altered. We are trying our level best to rid the neighborhood of unfixed cats but get no cooperation and all the Mom's seem to have figured out that we are good people and dump their litters in our yard. We currently have 11 "porch kitties" and five in the house kitties. The outside bunch lives in the garage with heat and shelter. We love them all but it is expensive!