I found a place that carries more "grits" in the 3M Trizact belts. They are closer to me too.

Supergrit:

http://www.supergrit.com/products/products_belts-misc.asp

1" x 42"
They carry A16 (1000 grit), A45 (280 grit), A65(220 grit), A100(150 grit) also P180 and P400

2" x 42"
A16 (1000 grit), A45 (280 grit)

Mick