-Updates-
Tried SKS Longboard, Planet Bike Speedez, and PB Cascadia fenders. All three worked fine for the rear wheel, but the Cascadia required the least amount of modification to accommodate the front wheel's disc caliper. The quick-release Speedez would have been ideal, but the Vaya's fork (offset at crown rather, than raked at dropouts) wasn't compatible.
BTW, the Planet Bike fenders install quite easily. They come with the stays pre-installed, and require very little in the way of adjustment.