Maybe this will be a little more up your cul de sac....
There's a group called ICDC Publishing looking for writers for textbooks for vocational schools. They suggest you go to their website,
http://www.ICDCPublishing.com and get the writer's guidelines there. I don't know how much they are paying for writing textbooks, but it might not hurt to bop over there and see what they're looking for. They welcome query letters via email. The address is
ICDCAuthors@yahoo.com
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My primary criteria for sharing these things are that they don't require you to be anywhere in particular (so the ones that require you to be living in Japan or Detroit I don't bother with) and that they look at least remotely interesting to someone, even if not to me.