I use Divoza half pads they are good and not that expensive
I would recommend le mieux as i have loads from them, from boots to pads, I wouldn't say they are that cheap but the products are very good quality!
There are many reputable half pad brands. Depending on if you need shimmable, sheepskin, fun colors etc, the brand with depend. Matts, EquiFit, Ogilvy, ThinLine and ProLite all make high quality halfpads that can cater to what you need specifically. Often times, the first place to check for these half pads are Facebook sale pages or local tack shops, for used but not abused half pads! Hope that helps!