re: 5 1/2" Spindle Sander Sleeve availability

Somewhere is a treasure trove of both diameters and grits. Having as many partial hits as I saw it's just a matter of someone selling, doesn't have an idea of how to work a search engine, which makes finding their offerings an issue. I am not the person with expertise in how to do that, but savvy sellers know how to get their offerings searchable, so a search like you did gives results to the whole Enchilada.