Broken nut

Part of the nut broke, and I'm trying to find a replacement. Checked some stores but none had bass nuts, so looking online now.

The size seems to be 1 9/16 L, 3/16 W, and 13/32 (something like that) H. The closest size I can find is the ""GRAPHITE SLOTTED NUT FOR GIBSON BASS" on this page
http://www.guitarpartsresource.com/bass_nutsaft.htm

Anyone have experience with these kind of things? Any other sites I could check? (All parts did not have any that fit the length and width). I could just get a 5/32 width nut, leaving a 1/16 gap. How bad would this be?

All measurements are in inches, sorry if it was confusing

 

Thanks! Sandpaper would be fine, right?