Hi, I don’t know about the bench type ones, but I would think they have a linked belt also, so you don’t have to take the machine apart to change the belt, but with the under drive type, the belt to the spindle can only be tensioned by removing a link or two, from a linked belt, as there is no adjustment between the intermediate shaft and the spindle shaft, and dismantling the machine to fit an ordinary Vee belt would be a much more involved job to do, even if you could find one the right length.
I can’t ever remember seeing a leather link belt, but that doesn’t mean they don’t exist, all the ones I’ve had anything to do with in my day jobs, were made from layers of impregnated and bonded together canvas with a rubber type material.
The link above is an old one that was on my Myford M type lathe, which is one size to big and has five canvas layers.
Fenner belts have been in use in industry for years, and are among the well respected manufacturers. They may be pricey, but will most likely last very much longer then the cheaper versions, and I have heard how some of those cheaper types do stretch over a short period of time. There are other good reputable makes though, but their price may not be much different to the Fenner ones.
Regards Nick.