There is an interesting strop listed on eBay OLD RAZOR STROP IN A BOX WITH INSTRUCTIONS!! - eBay (item 310190360603 end time Dec-29-09 17:04:09 PST)

I have seen one in a local antique shop, but couldn't see exactly how it works because the belt was quite stiff. I know that there is a slot to slide your SR into it and then alternate pulling on each end of the belt.