The belt should last for years. No reason to hurry and replace it. but keep on the lookout for canvas or nylon "web" belts that might work. They might not be listed as vegan. And some do use a little leather as trim. but a good web belt is what I think you should be looking for. IMHO, they make a lot more sense than the traditional braided leather belt that is part of so many uniforms.
I guess what kind of boots are required is important. Steel-toed? how high? Soles?
Anyway, for years and years, Doc Martens was the only vegan shoes available. and they still provide a really good variety of vegan workbooks.
-https://www.drmartens.com/us/en/mens/vegan/c/02060000
Here is a good resource
-https://veganmenshoes.com/vegan-safety-work-boots/