How Christian.
Borrow a trap from the nearest rescue or spay and release program. Once caught, take it to them and they’ll spay the kitteh and try to find a home for it.
Or do what I do. Grab the kitteh. Keep him isolated from you’re kitteh. Take him to the vet to see if he’s fixed or has a chip as well as healthy. If not, get both. Bring home kitteh and add to your collection.
Someone smack me. Your not you’re.