I just got my new Keter folding workbench today for use as a portable shooting table and it looks promising. It's not as stable as concrete, but a lot more portable. I got this one from Northern Tool because it was the only model that I saw with the extendable legs that give it the full 33.7" bench height (I was going for 34"). It goes from fully folded to fully deployed in seconds. I have some 3/4" plywood to make a better top for it, mostly so I can get some overhang on the back end to keep my knees and stool from hitting the bench when I address my rifle on the Caldwell rest. Cool thing is the bench comes with a pair of quick clamps that store inside, perfect for attaching the plywood top. And it's not JUST a shooting bench, I can use it around the house for chores. Anyway, not trying to shill for Northern Tool, just thought I'd share the link to the product for interested folks to check out. It's on sale $20 off what I paid for it, figures....
https://www.northerntool.com/shop/tools/product_200803851
https://www.northerntool.com/shop/tools/product_200803851