I'd speak to your local avian vet about it. At that age, nothing is guaranteed, but if you want to go down that road, you will need a vet's assistance. In addition to surgery I do know that it's possible to chemically castrate a cockerel. The only thing is it may affect your ability to eat him (although that doesn't seem to be your plan anyways). Whether it's worth it or not in your case, I couldn't say, but I'd lean towards probably not, but if it's indeed your desire to caponize him, then you'll want to get on finding a vet to help with that immediately although you might have a tough time of it as it's hard enough to find a vet who sees chickens at all and I couldn't tell you how expensive it'd be