There aren't many different layouts for the model m. If you venture to the model f series then there are various layouts, however unless you get the highly elusive kishaver you won't find anything small.
Pretty much all boards in the model m series are the same. Some say the ones with grey labels are nicer however.
OMG Frosty! Your Avatar! What is going on here?!?!?!? Shark infested waters!
On subject, you can get the Model M in several flavors, but be aware and avoid the rubberdome versions. They usually start with a model number 7xxx. You can also find them on ebay for a reasonable price, but be aware that prices fluctuate wildly there. A good start, like Fohat said, is the 1391401. You can also look into the 1390120, 1390131, 1398601, 1370477, 1394540, 51G8572, and the 1393464.
Beware of terminal boards. You can get them and convert them but you have to get a 1391401 (or equivalent) controller and an SDL cable. (Keeping that in mind, the price you paid for that "inexpensive" terminal board may have doubled or tripled after doing that.)
* You can also see pictures of my Model M's in my Sig. *