Rugged cycles seem to be the supplier. All the bikes I looked at had LLNL logos on them, and no vendor markings. RC's web site isn't geared for retail. They appear to be aimed at selling fleets of bikes configured however the buyer wants.

The linked PDF is from the lab's internal web. I will say that the initially specified solid tires didn't go over well with riders. The motorcycle style two legged kickstand was dropped as well.