I have used the Purple Ultimate Seat Cushion for years now and swear by it. Can't remember what I paid for it, probably used Pilot points anyway. Beware of knockoffs on Amazon
It’s a company called purple. I tried one and didn’t care for it at all. Mine was a free knock off from the company though.
Tennis ball method works. Also, no wallets in back pockets, and try not to cross your feet when you sleep.
https://www.swifthealthchiropractic.com/sciatic-pain-and-a-tennis-ball-what-they-have-in-common/
I'll just get five of this. That'll work.