I found this easy to follow neck pillow pattern and made it into a wheat bag.
I made an X large for my husband and a large one for my teenage daughter.
They heat up quicker than the fabric wheat bags. The link to the pattern is below.
Dont let all those pages put you off they are just instructions for different sizing.

Neck pillow link.
http://members.aol.com/cillcrochets/neckpill.html