Silvan notes:

I have looked into a few though, and they don't seem to make them small
enough for my site.

Smallest is 21' x 28'. http://www.ironbuilt.com/ib_specials.html

If I'd know about these when I built my shop....

Charlie Self
"Abstainer: a weak person who yields to the temptation of denying himself a
pleasure." Ambrose Bierce