That looks like a standard pot metal pulley that you can buy at any hardware
store. If it has lasted a long time then maybe that's all you need, however .........
I had one of those on my Onan genset and it about drove me nuts trying to keep it tight on the shaft. If I forgot to check it regularly it would wobble loose, wear the pulley bore and then eventually fly off the shaft. Fortunately the Murphy switch would then shut down the Onan but it was a major PITA. I'm off the boat right now but I have a replacement pulley with a compression
hub. They're not easy to find in small diameters and narrow belt widths but they are available. You'll have to find a power transmission
house - someone who specializes in conveyor parts
would be ideal. It took me a while but I found an image of what you are looking for - you don't need the multiple belt grooves but you'll get the idea. I call it a compression
hub pulley but the partsman at whatever counter you find may have to impress you with how smart he is by calling it something else.