Cat on a hot tin heating vent

Aww, your cat feels cold. Here's a site with some suggestions. 

I'm sure there is a more elegant solution, but the first thing that popped into my head was these:

Grid Wire Modular Shelving and Storage Cubes

http://www.bedbathandbeyond.com/product.asp?sku=16719773&utm_source=google&utm_medium=organic&utm_campaign=shopping

You could build an enclosed square (or rectangle depending on the length of your vent), and place it on top of the vent. It would be open as to allow heat to escape, but you could put a folded blanket or towel on the very top and it would be a nice place for your cat to lay without blocking the vent. I'm pretty sure that they are metal and would be ok with the heat. I know that target, walmart and the likes sell a set for not too much.

Since you mentioned the vent sometimes gets stepped on, I am assuming you are against any method of covering it up, such as this?

http://www.installerstore.com/Air-Deflector-w-Dust-Filter-for-Floor-Vents-Registers.html

My parents have those on all their vents, and you can hardly notice they are there since they are clear. However, all of the vents in their house are next to walls and behind strategically placed couches (yep, the vents are STILL babyproofed for me 24 years ago), so they don't have the possibility of stepping on them.

Since stepping on them is an issue, you could try putting some citrus rind, or something else cats hate the smell of, around the vents. This might deter your cat from wanting to sleep there.

Also, is there any possibility you could buy a heated pet bed? If you block access to the vents temporarily while keeping the heated pet bed plugged in, your cat might decide to switch from the who-knows-when-it-will-turn-on vent to a permanently warm bed. Rather than stop the behavior of craving warmth, you can redirect it to the cat bed.