Wonderful job, All! Thanks so much for your suggestions and personal reviews...this is just what I was hoping for!
I had an errand to run at REI yesterday, so I stopped by their bicycle-accessory department (always a requirement for any trip there and looked to see what they had. Sadly, at this time of year, stock was pretty well depleted, but they did have on-hand the road version of the Topeak Turbo Morph Julian mentioned. It looked very nicely made, and my concerns about the longevity of the hose appear unfounded (I was thinking the rubber might deteriorate quickly in the desert sun and heat...but it appears to be plastic, which woud likely last longer). It could always be "de-silvered" with some suitably large black-colored heat-shrink tubing. So, a possibility, for sure. The only thing that really gave me pause was the foot-rest. It is plastic with a teeny-tiny little retainer hook that looked as if it might become embrittle in cold weather. My concerns are probably unfounded, but that did catch my eye as a potential trouble spot.
There just one Lezyne there, a tiny thing about the size of a highlight marker pen made of carbon fiber. Beautifully constructed, so I can say I was impressed with the fit-and-finish and should investigate their other offerings (like the Floor Micro Drive HV Pete, Martin, and Lemming referenced).
As an old-school roadie, I am particularly fond of the Zefal HPX series of pumps. I'm saddened to think they're no longer made, as Andre said. I knew the black ones had been discontinued in favor of silver, and they still appear in the Zefal catalog...but have been dropped by SJS Cycles. I might be able to source one in the right size from eBay. I have the HPX2 from Sherpa and two or three spares I laid-in for future (one sourced from a shop in Ireland!). Once the 590M Nomad arrives, I will have a much better idea of it is possible to fit one to it behind the seat tube. I doubt I will have clearance for one in the same location, because the Nomad will have a shorter seat tube. So, it may be I need to either sell what I have or keep them for spare parts and seek a shorter HPX1 if I go that route. I realize the Zefal HPS is a "long and skinny" pump and therefore not particularly suited to relatively high(er)-volume, low(er) -pressure use on my 26x2.0 Schwalbe Duremes...but I do like it, it is familiar, and really long-lived. Rebuildable, too, provided one has some spare parts laid-in. Andre summed up my feelings about it nicely when he wrote...
A mini-pump is by its nature a compromise. I have a hard time believing you can beat the HPX, which is a proper pump if short, if you can fit it (I can't). It doesn't bother me that it is out of production: buy enough service parts to see you out.
Still, if one cannot be found, or is too long even in the smaller (HPX1) size (I have available means to mount them), then I will need to consider the best of the mini-pumps to substitute. I'll be looking closely at the ones mentioned above and the Topeak Peak DX.
The reason I was looking at the "convertible floor pump" versions is the shorter length and smaller barrel diameter couple with high-volume tires means an awful lot of pumping compared to a skinny road tire and pump. Though I've never had a problem sawing through my valve stems, I can see it being more likely when a lot more strokes are required.
Any other candidates come to mind, or further thoughts and suggestions?
Thanks so much for the help; very much appreciated!
All the best,
Dan.