The photo shows a totally bland, all-beige keyboard, but if you want to be authentic old-school, it needs to have the traditional beige/gray color scheme (aka "pearl" and "pebble" in Unicomp lingo).
There is really no logical choice except an IBM Model M/F, but the Dell AT101 would look right at home. I disagree with the Apple boards, they are nice, but Apples are distinctly more yellowish or brownish than true IBM beige. Weight and size could not be an issue, since the rest of the gear is monstrous as well.
Thrift stores are probably your best bet for components from the previous millennium, and cheap also, but you will get much better stuff on ebay, if you are willing to pay the freight.