I was attending MacWorld Expo in Boston a couple of years ago and happened upon a booth with people selling products branded as Nada Chair. Their products provide lower back support and the design looked interesting to me. Straps extend from the padded back support and loop around your knees. The little pads and straps didn't grab my attention but then I noticed vests with similar knee straps.
The only one they had left happened to be in their largest size. It fit me perfectly. I believe I paid something like $100 for this thing and it has been worth every penny. The one I have (olive-khaki) has a bunch of pockets (14 according to the web site) great for holding connectors, HTs, repeater guides, copy of my license, cell phone, pens, mini log book, and so on. It is constructed of strong material and seems like it will last forever.
When I'm sitting at a picnic table or other seat without a good back support, I just pull the straps from their little pocket and loop them over my knees. You might even hear me say "ahhhh" when I do it. The lower back relief is instant and I can sit for hours like that racking up the QSOs.
If you have problems sitting places that have insufficient lower back support I suggest you try a Nada Chair. There are many models and they are even sold on Amazon.
Waldo's saga: In apparent retrograde motion, Waldo has made a return to a Connecticut FedEx facility. Delivery estimates say it will be here tomorrow.