Print 4 to a page off (a6?) guillotine them nicely, bulldog clip at the top to square them up and a bit of carbon paper underneath to copy the signature through.
Cheapest way.
Or, ebay has loads of printers doing business cards for next to nothing. £41/1000!
I'm sure if you had a word they would print whatever you sent to them. Most of them seem to need print ready formats.