Heated bed mount is warped

Hi folks,

I put my single sheet Prusa i3 together from a kit and used it for a few months. I had assumed that (what appears to be) a wooden frame would be good enough, but I was wrong.

The frame itself is fine, but the heated bed mount is badly warped, so much so that it makes leveling the bed impossible.

The bed actually bulges at the middle, and is lower on the sides, much like a covex mirror. The sheet of glass does not sit flat on the bed. The clips help a bit, but not much.

It's quite sad to be honest.

What is an actually good material to use for the heated bed mount, and where can I purchase one?

Thanks!

There's a few on ebay, beds only running around $20 or so dollars. Just search for Prusa I3. It'll show up somewhere on the search page.

Thank you!