Shucks. If I'd noticed this thread first, I would have posted here instead of the OT post in BB's thread. Here's the relevant info:
The Topeak WB mount is not on their website. It just so happens that they make the mount for another pump and it works with the RoadMorphG series. Call Topeak Customer Service to order the special mount. Should run about $5 plus shipping.
"we have a mount that can be used on WB cage - $4.95 plus S&H. To order please call 800-213-4561, press 2, 9-5 pm EDT, M-F"
Mine should be waiting for me when I get back from vacation. I'm anxious to try it out (and get my 2nd water bottle on the bike)
FWIW, I tried a Blackburn mount, but it wasn't the right size for the RoadMorph and although the velcro strap would tighten down to hold it, the WB cage seemed to interfere with using it.