Is he neutered? An intact male might not get along with a spayed female as he may just want to hump her and be a male rabbit. 2 males rarely get along, even when both are neutered. If he is not neutered, it would be best to get it done and wait 4-6 weeks for the hormones to calm down before you try to fine a friend for him.
I would try for a spayed female. He might get along with a neutered male, but it would depend on the individual rabbits.
If you have a rabbit rescue (or a shelter that has rabbits), you probably could arrange some bunny dates. You wold take Milo and he would get to meet some other rabbits. You can see if he likes other buns and if there is one that he really likes and you could adopt.