I just went thru the same thing in a firepower I'm restoring. I posted a WTB ad here and a fellow pinsider actually sent me one for free and I paid for shipping. There's probably someone around sitting on that very part. I'd post a WTB ad.

If I hadn't been able to source one I was actually working on creating 3d models to print the light baffles so I could just make one out of plywood.

Make a new one out of plywood or particle board, or hunt around for one that came from a game that was parted. Interestingly enough, I had the exact same issue on my hulk. I managed to find a replacement after a few months of searching.

My Joker Poker had some swelling similar to yours in 3 of the 4 corners. Take a razor blade and trim it close to the level of the board and then sand it down to blend it in.
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mine on hulk was also swollen and warped. stripped everything off it and used it as a pattern to make a new one from mdf.