I just bought one of these: https://www.amazon.com/Orthopedic-Tailbone-Sciatica-Pressure-Washable/dp/B08B7ZHKLN/ref=sr_1_9?crid=5GB9MXM4JLGY&dchild=1&keywords=back+support+office+chair&qid=1623197666&sprefix=Bac%2Caps%2C197&sr=8-9

It’s designed for lumbar support. It’s cheaper, and isn’t permanent, so you can switch chairs. The link above isn’t the exact one I got, but I love mine. I can take it to the couch or the car if I’m having a tough time, and it’s outlasted 3 office chairs.