I use the $20 one from state line tack right now but I’m really looking at the Total Saddle Fit half Pad with wither freedom
Use a saddle riser. It's made out of a soft/hard memory foam that doesn't sink down on the horse. U can get them at greenhawk.
I am currently using a sheepskin and it's rubing badly
I’d avoid thick memory foam pads because they could press down on the whithers. Many sheepskin halfpads will probably work pretty well