Top tube protectors

Here's a radical thought, look at the Kashimax TT protector and see how it is made (a strip of metal coated in rubber), then reconstruct.

If I were to do this I would;

Cut one or two strips out of a can (a soup can or similar as it's thicker than a coke can).

Put electrical tape on the frame to protect it from the metal strips and secure the strips with more electrical tape.

Then for aesthetics cover with any excess bar tape like in the picture the OP posted.

It may look bulky but your TT probably won't get dented.

It's like Blue fucking Peter here.
Ride your bike. Scratch it. Dent it. Break it. Buy a new one. That's how to get out of a recession...