sympathy post.
no seriously, i guess these guys are sick of this question, the search function on this site is the worst i've ever seen, so i can understand it gets asked alot.
http://dotheton.com/index.php?topic=3690
i believe ohiocaferacers gets their rollers from a place in italy, i've got the link somewhere. but they're muchos dinero, the Boretech KA tensioner is cheaper. and they have pretty much the best online customer service i've ever experienced.
in saying that, i was thinking of taking a couple of photo's of the tensioner with a ruler, and posting them up, because it's pretty basic, and if you have access to the machinery and teflon plastics, it would be easy to make. i'm not really sure if that's a cool thing to do though.