Welcome to the site Adrianne. I am glad that you are enjoying your new friend. You could probably get a couple of tank mates that don't get too big and don't cause too much mess. For example, you could get a couple of silver dollars and leave it at that.
Whatever you choose, choose very carefully, some fish get very big which wouldn't be good for you because your tank isn't quite big enough for a couple of very big fish. I would ovoid plecs, they are too messy. Some of the smaller African catfish don't get too big, no more than 8 inches.
I have got the absolute perfect tank mate here in my 125 gallon tank, you would absolutely love him and he would fit in just fine. He is a type of Jade eyed Cichlid. From what I can gather by looking him up in my books, I actually think he is a false Jade eyed Cichlid. He shouldn't get any more than 6 inches and is just a lovely little fish. He hold his own against the Oscars and just fits in really nicely. If you can't find one of these, you could just go for a normal Jade eyed Cichlid, they really are delightful little fish, you would love them.