Bike Forums - Source for 40 spoke, 650b rim?

Since there is no wheelbuilders forum, I figure this is the best place to post this inquiry.

I have an '80's Raleigh Portage - one of those that came with the 650b wheel size back in that time. The original wheels were 40 spoke rear, 36 spoke front. I will soon need some new rims. Of course, I could solve my problem with an entire wheelset replacement to get rid of the 40, but the original hubs are these pretty cool high-flange cassette numbers that I would like to keep using.

There are getting to be a fair number of rim options in 650b, but I have yet to find one where I can get a 36 and a 40 in the same rim. Velocity makes their Synergy rim in 36, and they have an off-center rim for the rear. I'd love to find something like this. Anyone know of anything available in both 36 and 40 spoke options?