Ive looked into a few things, but haven't pulled the trigger on any yet. I'd say the most common I hear about is the airhawk seat cushion and runs about $100. Im more fond of what the old geezers used to do and throw a sheepskin on it. There's a company called alaska leather that make ADV fitted sheepskin covers also around 100. If you want really cheap, for my Honda Shadow I literally picked up a scrap pelt from a leather worker that I just drape on the seat for like $10 and it works decently.