This is probably the quickest thing I've ever made, it took me less time to make than it would have taken to go to the shop and buy one. All you need is some aluminium sheet, a saw, a file, a hammer and some pliers. And 10 minutes of your precious time! Plus, even though it's not perfectly precision engineered, it looks way better than the plastic ones you can buy.
Start by cutting a rectangle of sheet aluminium. Mine was 1.2mm thick as that's what I had lying around. The size is not really that important so I didn't bother marking it up, but the dimensions are roughly 40x120mm. Check the pictures for more info on each step.
Once that is done, the edges will probably be a bit rough, it's worth filing the worst of it off just so you don't end up with bits of metal lodged in your hands later on.
Then put it over a sharp edge and use the hammer to bend it to shape. The sharper the edge, the closer to 90 degrees your bend will be. The only bend on mine that is not 90 degrees is to lip at the front, which is there to dig into the carpet so it has some grip rather than relying on friction. Again, dimensions are not important, just wing it based on the size of your door.
The final couple of bends could not be done with the hammer/edge method, so I used pliers, which gives you a less sharp bends and means you have to take some time to make sure the bend is even all the way across the part. It also scratched the surface on mine, but if you put a cardboard offcut between the jaws of the pliers and the part, it should keep the surface looking nice.
Last thing - remove the protective sheet and test! It held back a heavy door with a closing mechanism with no problem at all. Sometimes the simplest projects are the best!
This bending method applies to all sorts of stuff, I've used the same technique to produce a coathook that hooks over the top of the door as well as a phone stand.
Thanks for reading and I'm happy to talk about stuff in the comments or by direct message. Let me know if you make your own!