Depending on the thickness you need, I love thinlines for just a little extra between my saddle and my horses back, but if you want something a little thicker i like Ogilvy and Ecogold or if you are looking for just a normal sheepskin one, fleeceworks is great.
ogilvy, but if you're looking for something cheaper the acavallo half pads do a perfect job
ogilvy, thinline, mattes, ecogold
LamiCell! its my favourite and affordable!
Prolite pads, or kentucky or a Mattes sheepskin, depending on the horse.
ogilvy, thinline or any sheepskin half pad
Mattes are quite pricey but are great pads. Fleeceworks is a great cheaper option that does the same thing. However, I found fleeceworks are thicker pads than others. Ultra thinline are great too.
ogilvy is great but some horses react badly to it. one of my horses loves it but the other doesn't. thinline is also
Acavlio gell massage half pads are great but everything sticks to them!
I use an ecogold for my high wither ottb works wonders and it's easy to wash and adorable.
Ecogold and I've heard fantastic things about Total Saddle Fit!