Hi and welcome!
Your best bet is to take your boy to a good rescue for "boar dating", so he can choose his own new friend. The safest way is full (residential) boar dating, as in that way single boars of all ages can be bonded with a character compatible mate of any age and their relationship carefully stress tested before they go home, so the bond will be as stable as a sow bond.
Please make use of our list of recommendable rescues that has been given in a previous post; they have all been vetted by the Piggy Bank rescue support network. The vast majority offer either full or speed dating (the latter is just an afternoon of short meetings with likely, mostly baby boars and therefore somewhat more subject to later fall outs when the youngster hits the big hormones).
Personally, I can most warmly recommend Crawley GP Rescue; they offer full boar dating.
http://www.crawleyguineapigrescue.org/
Here is a link to a "dating blog" a rescue lady in South Wales is kindly keeping for us; you will get a good idea of what is involved in full boar dating. All of her bonded boars are still together, by the way!
http://www.theguineapigforum.co.uk/showthread.php?t=59233
As to neutering - your boy is not the youngest, so it would be even more paramount to find a very good and experienced neutering vet in order to minimise the sadly not inconsiderable risks during and after the operation. Your boy will also face a full 6 weeks' post op wait until he is fully safe to be with a sow. (I have a surprise baby from a newly rehomed sow who spent two days on the lawn with a supposedly "safe" over 5 weeks post op boar, just to prove that point! I have also been through a very close shave with the only boar I had neutered on my own account by a local vet, and sadly I am not the only forum member with a bad neutering experience; I can't stress the importance of finding the right vet enough!)
Here is more information on neutering:
http://www.cavyspirit.com/neutering.htm
PS: Spayed sows are sadly as rare gold dust, as a spaying op is more invasive and risky than a neutering one. There is only one rescue in Rugby (RNGP Welfare - also on the Piggy Bank map) that spays as a matter of policy, and they depend on incoming piggies, so there can be quite a waiting list.
