The Asolo 535s are actually still around聴they’re now called, in a clear case of Tech-Sounding Name Inflation, the AFX 535 II. Price is $160. It’s a classically designed boot: one-piece leather uppers, padded scree collar, Vibram sole. Thankfully, no waterproof liner聴something you’re not likely to need in New Mexico, even with summer monsoons. Leather thickness is the same as your old pair (2.2 mm to 2.4 mm), which falls in the mid-weight range.
My thought is that if you liked your old Asolo 535s, why not get another pair? I think they’d be fine for that part of the world, even for much longer trips. Or, you could try Asolo’s new boot, the FSN 95 GT ($150), which has been wildly popular as both a day hiker and backpacking boot. I tend to think the Montrail Vercors ($190, but discontinued despite frequent glowing references to it by Yours Truly) may be a little heavy for you, although it’s a fine all-around boot. The warmth issue is neither here nor there聴by the time you don socks and all-leather boots, your feet are going to heat up, regardless of whether the leather is 2.4 mm or 3 mm thick.
You might also look at another Montrail boot, the Torre GTX ($150). It’s a nice, mid-weight hiker along the lines of the FSN 95. But, like the FSN 95, it has a Gore-Tex liner, and I would think that could definitely lead to hot feet. Best, perhaps, to go with something like the AFX 535 II or the Vercors聴a straight-up leather boot without a waterproof liner.