This is a tough request. I think it all depends on your standards for rigidity. Almost any bench will work for 1" groups. But if you and your rifle/ammo are capable of shooting 1/4 MOA, a solid rigid bench is imperative. There is a reason the bench rest crowd shoots off of solid concrete benches......
I've gone through many iterations of building a solid portable shooting bench - each better than the one before. Most have become workbenches instead of shooting benches because they just didn't measure up to my needs. My most recent bench actually worked fairly well, but you need a football team to move it. So it's permanently installed at my range out back now.
My next bench will have a solid welded aluminum triangular box frame with cross bracing and an adjustable rear leg for leveling. It will have a removable top made from two layers of 3/4 inch plywood dressed one side for the top. The top will have some kind of 3 point cinching mechanism to attach it solidly to the frame. That's the plan........
The only commercial bench I've ever used that was even remotely usable (for my needs) is the Stucky bench others here have already mentioned. But it will cost you.....
