Opteka makes the Opteka X-TREME .3x fisheye. Its like 80 bucks on there site but can go for like 30-60 used.
Then you get a cheapo no name (or opteka) .48x fisheye, whatever its called. Comes in like 36mm usually. those little baby silver shitboxes go for like 15 bux. You unscrew the elements and use just the curved piece, hot gluing it into the back of the opteka xtreme just like you would mod a raynox
Boom same look and distortion as the raymod