Where to find a smaller keyboard?

Well, although Apple's "Pro" keyboards are some of the most compact full-sized ones you can get (almost no border), one cheap option would be to get your hands on one of the old iMac-style Apple keyboards. Those aren't the greatest keyboards in the world, but they should be quite cheap used (eBay or such) and lack the central stripe of "page up/down" keys, so they're significantly thinner.

Most of the other compact keyboards I'm familiar with have undersized keys, which is hard to type on. I've bought "flat" keyboards with a built-in trackpad for use in trays on rackmount systems, but those are usually full width.

 

http://www.frogpad.com/

 

Adesso makes such a thing, but I believe they are laptop size keys.