I've got one of those Peak 8x loupes and 2 Pana Vue viewers.
The peak thing is fine and it does its ob...the only problem are the slightly soft edges and you might have a hard time noticing if the focus is sharp if it is ever-so-slightly off.
The Pana View things are good to use as a portable lightbox in the field, but thats about it. It's very tedious to put one slide at a time.
Plastic loupés are just absolutely awful (not particularly good for eyes, either).
My Ilfochrome printer uses a focus-scope for examining trannies.
A 4x loupé is too shallow to critically discern detail. Go for 8x to 10x.
A Nikon 8x aspherical loupé has done the job for me for about 20 years I think; no idea where I brought it from but possibly overseas. It's all glass and no chromatic aberration during viewing. Schneider makes some truly excellent loupés but they are mega-expensive ... around $500 for an 8-10x, still, they are the bees-knees in build and viewing quality.
If you have defective eyesight, a loupé with dioptric correction may be useful.
We know you're six hours from a camera store, but in what directioin? IE:where are you?
Take a look at the auction site or craigslist