The virus doesn't live outside the host and can only be transmitted cat to cat. Bleach the litter box to be extra safe but you should be able to bring in another cat without any delay. Check with your vet to be sure.
I'm sorry about the loss of your kitty. Thank you for giving him such a good life.
The conventional wisdom is to wait 30 days to be 100% safe.
However, the risk is virtually zero after just 48 hours. The virus dies quickly outside the body and is susceptible to pretty much all routine disinfectants.
I would replace all soft things used extensively by your old cat (e.g. beds, catnip toys), or wash them and put them in a bag in a closet for a month before bringing them out again. Dishes and litterboxes should be replaced or thoroughly disinfected. If you do these things, I think you will be more than safe if you wait a week.