If it is quick and dirty you need seems like you could stamp one out with some heavy foil. It would likely fit better than anything you could buy. This is only my tow cents, However, good luck.
I'm with xray... I would cut a quick and dirty die stamp to make your own shield. If the numbers are in the hundreds+, it would be more cost-effective to have someone else cut it.
There are several photo-etching and laser-cutting companies that will make EMI shields. One or more of them a few years back had some standard sizes. Some of the companies have been mentioned already. Here are some more.
If it's sensitive enough to need a shield, it's an RF circuit... a receiver, in point. Just because you didn't design it to be RF in nature doesn't mean it isn't...
I found once an asian electric fence circuit with just a piece of PCB laying over a square made of thick copper cable, all soldered down to the PCB power plane. A desperate measure, though all parts inside the area were RF/dust/moisture safe