You can also order them via the supply system. NSN: 6675-21-902-4737 for a larger 10" x 4" or NSN: 6675-21-880-9689, for a smaller one that fits in your FMP (order two as they seem to get destroyed over time).
or
LPO / personally puchese these items from Visual Planning Corporation Ottawa - Phone: 1-800-361-1192.
Much more reasonable then the cost of the "auto google" from Australia that came up in the link above.
http://www.visualplanning.com/ - click "Government Military and Tactical" on the products page and then search under templates "traffic accident and military".
I am quite fond of item VP 425-8125-MMS, but there are some of the other ones listed in this thread (including the APP-6A type one). They also sell the CF type protractor, The prices are not bad.
MC