I am not sure why you prefer a mechanical.
There are advantages, sure- but mostly in terms of speed. There was a now deceased guy who I respect a lot on this forum who swore by mechanicals- for production work. He had stops set to punch holes in hundreds of base plates a day, and said the return time of a mechanical meant dozens more plates done per hour over a hydraulic.
But for small job shop/ornamental, a hydraulic is much nicer, in my opinion- because you can locate holes much easier, and more accurately, by slowly lowering the punch until its close enough to locate a center punch mark.
Also, a hydraulic machine is less likely to break if overstressed- usually they just stall, while there are a lot of cracked buffalo's out there.
The Buffalo is sturdy, and simple- its almost a 100 year old design, although there were a few version changes over the years, with the last ones using a fabricated frame rather than cast iron. They are technically still in business, but I think they are pretty small these days. Parts for older machines will be scarce and expensive.
The Mubea and Peddinghaus, both german made, are newer designs, more elegantly made, in my opinion, and have the same reputation of being bulletproof and longlasting as the buffalos.
If I was shopping mechanical, I would probably be looking at Mubeas- although they have been all hydraulic since the early 70s, so you are looking at a 50 year old machine, most likely. Again, parts are mostly not available- they are just too old.
There are three punch and die makers in Cleveland-
American Punch Company - The Punch, Die, and Shear Blade Experts
Ironworkers, Punches & Dies | Cleveland Steel Tool
Cleveland Punch and Die Company - Home
they all make most common punches, but sometimes one is better than another for oddball stuff.
these guys, in Kentucky, know a lot about Mubeas- and you can call and pick the brain of the parts guy about whether a given model is worth buying- I once almost bought a really cute 1958 Mubea Mechanical, until I found out how rare any parts but blades and punches would be.
mubeamachines
I am a big fan of Geka's myself, I think they are the nicest machine for a small shop that is always doing different things, and they have the best gaging and stops, which save a lot of time and make for more accurate locating and lengths. But they do cost more.