Occasionally you see vintage pump leathers on eBay, but the models and sizes make it fairly hit and miss.
You might look to see if there is a Tandy leather shop near you. Or any leather shop for that matter.
Take your old one off and take it in there. Find a proper thickness and size. I'd get an extra piece just in case.
You'll have to size it yourself with scissors or a hole punch. It needs to be a bit larger than 32mm. They kind of have a cupped shape. That's why I'd get a couple pieces, so if cut too small, try again. I'd probably start at 34mm.

Short of that. Saddle soap, Brooks proofide or 30w oil might bring it back. Depends on how hard it is.