I bought a T-Wrecks for cheap off ebay. I didn't notice anything missing in the listing, but when I received it I realised it was missing a neck flap. And yes, it was missing in the listing now that I knew what to look for.
I wasn't too bummed: I mainly wanted it for robot mode, and in dinosaur mode I could scrunch the arm up so the gap wasn't too noticeable.

But I love a challenge.

So I needed something that had a textured surface that I could easily cut and bend into shape. And my mind drifted to a pack of cheap plastic zoo animals I had bought for a Beast Wars custom.
I ended up cutting apart a lion and eyeballing a shape to fit. And then colour matching, which I think I got pretty close to.

I've seen T-Wrecks described as red but the best colour to match it was actually orange.

I am going to tinker with robot mode, but that's more a custom than a repair.