This article is from the Feline Leukemia (Cats) FAQ, posted to rec.pets.cats newsgroup. Maintained by Erin Miller with numerous contributions by others.
There a few options. The only thing which you really ought NOT to do is get a healthy cat as a playmate or let your cat outside for excitement. Dogs cannot become infected with the Feline Leukemia Virus, and some dogs and cats, especially those raised together can be very close. One word of warning: getting a dog (or any pet) for the sole reason of keeping a cat company is not a good idea. If you consider getting a dog, make sure you understand the amount of time and responsibility that goes into caring for a dog (which is much more than that of a cat); otherwise you will regret the decision and both you and the dog will suffer. (There are excellent dog FAQs which will give you as much information on the matter as you can handle).
Another option is getting a second FeLV+ cat. The obvious down side is that you not only have twice the vet bills, but you also put yourself at risk for twice the heart-ache when one or both become ill. However, if you are willing to take the risk you can search for FeLV+ cats by putting an ad in the newspaper and calling all your local vets and animal shelters and explaining your situation. They may put you on a list and should they receive any cats which test positive, they may give you a call. Make sure you give your current vet as a reference as most shelters and other vets will want to make sure you understand the responsibility of owning an FeLV+ cat or to make sure that you are not some psychopath looking for sick kitty-cats to do nasty things to (of course most people, especially your relatives, will think you are a psychopath anyway, for keeping and seeking out more FeLV+ cats).