Always something new...

So I am recruiting assistance for my latest project - hope you can help.

My desk is 21" x 48" and I have a map I'd like to cover it with. My reason for wanting to do this (other than the fact that I love maps, of course) is because the desk is a hand-me-down, beat up and aged old friend. It has seen better times. But after months and months of considering trading it through Freecycle.org, or building one from old shipping crates and a weathered door as the table top, I've decided that keeping what I have is the way to go. I'll change the handle hardware, etc, but a glass or acrylic table topper seems to be too expensive. Decoupage seems to melt when under laptops (as I've learned the hard way), but is it save to sit a desktop computer on? Will either suffer?

And remember, I am on a budget. If not decoupage, what wallet friendly way can you suggest to protect both the map and the electronics on top?

-L