I’ve got some very old (read very drafty) windows in a bathroom renovation that I am currently working on.  The sashes seem to be very sound and the glazing is that antique wavy lead stuff… so I’d like to keep the sashes if at all possible. 

I’ve seen products on some of the DIY shows that retrofit the sashes to use a track instead of the pocket weights but I can’t seem to find them anywhere.  Does anyone know of a manufacture of this type of product?  Any recommendations?

-Steve