How cheap is cheap, there are lots of them in scrap yards. I'd check your local yards before buying on Ebay just because shipping is a killer on something that shape and size. The yards here generally charge about $25 for a cluster out of an older focus. I'd offer to get you one, but ours are in KM/Hr, the MPH is very hard to read.
There are also 3 different clusters you can get
one with normal black face,
the SVT which is white faced
or there is another greyish faced one I have seen, it looks like it might be translucent.
Here's link to a how to on changing the gauge faces, but you can use it to figure out removing and install the full cluster (just don't use the part where you open the cluster)
Edit: might be handy if I actually include the link, LOL