Here's a lens I found on 3dlens.com

http://www.3dlens.com/shop/ohpfresnellens.php

I recently warped my 220mm and 330mm fresnels, so they need replacement. $60 total. This lens seems to me like it would do the job of both lenses for $40. Note that my old lenses were unsplit, so no problem there.

The groove pitch is wider, and the whole thing is 4mm thick so I'll need tools to cut it, but apart from that is there any reason why it wouldn't work?