We recently found a new home for our mare. (that was sad, but she is perfect for what they want. She wasn't working out for what I wanted to do) I was worried about our yearling gelding, he was so attatched to her. I won't be looking to buy another horse I can ride until next year. And having just him gives me more time to work with him and get him doing a lot better with ground manners before taining next year. So we decided on a mini horse for company. We got one the same age as him, and my lord are they cute together! I think Bolt is estatic to have another young horse to play tag with. I don't have to spend the time on a mini like I would with another bigger horse. He is a good little guy for my little boys to learn some horse things with also, man was it cute when my 2yo was leading him around! He cracks me up when he runs too, those little legs going. The stud at the place I got him came charging at me to defend his little harem, and that was just cute also. Took him forever to get to me! haha.
Anyway, just a plug for a mini companion. Maybe a little more work than a goat, and you do have to do their feet like any horse. But the cuteness makes up for the small added expense. We considered a goat as well, either would be better than your guy being alone.