I’ve used a couple of different makes, they’ve all worked fine. I prefer Ceramic ones, they seem to last longer. I’ve not tried Trizact or Diamond though. The Axminster and Sorby belts are interchangeable even though there’s a 5mm difference in length.
The cheapest I’ve seen so far is Abtec, but there is a minimum order.
[URL unfurl="true"]https://www.abtec4abrasives.com/50mm-x-785mm-ceramic-cloth-sanding-belts-per-belt-11703-p.asp[/URL]