I'm confused. You say your TM is missing that piece and you want to build one. But you posted pictures of it. If you actually decide to build one, it won't be difficult, except that it will be hard to match the color/texture of the finish, and it will be hard to duplicate the contour of the edges unless you have a router and a bunch of bits.If it would help, I can take pictures and measurements of mine, but my TM is closed up in the garage and won't be accessible for a couple months. Perhaps someone else can help you sooner.
Incidentally, it would be better if you don't post your photos on an external photo-hosting site - in your case, Amazon. The day will come when either Amazon will stop hosting photos and take the storage down, or you will stop being a member of Prime. Either way, your pictures will immediately disappear, and be of no use to anyone. Instead, post your pictures right here on the forum. One of the purposes of this site is to build up a body of knowledge about TMs, and pictures are an important part of that. We want to keep them.
Posting here on the site is easy. Take a look at
https://www.trailmanorowners.com/for...ad.php?t=16117
Thanks
Bill