We have two of the H-D Circulator seat pads as well as one for my rider backrest and they really do a great job of keeping you dry on those long, hot rides.
I've used mine quite a bit in the last several years and it still looks like new.
I bought this same air flow seat cover for $40 at a bike rally a couple years back. It works great, the first time I put in on it was around 100F, it felt like my butt was wet it was so cool.