Collectors Pocket Loupe 10 x
This is a typical Collector's 10
x pocket loupe
Of course this is just a sample. If you do not mind, you could also carry a regular watchmaker's loupe (Bausch & Lomb's 4x is praised by many as the standard for this purpose). The regular watchmaker's loupe will give you of course more aperture, but to me that small size is preferable and the fact that the lens is protected. I found those Japan made loupes here in Bangkok for THB 40 to 60 depending whether you buy them on a street stall or at the watchmaker's shop. But USD 0.90 to 1.40 is not a bad price for this very useful tool that just has to be in my pocket, together with my A&F case opener knife. But since 911 no more traveling with the case opener knife, it will stay at home, because I never travel with check-in luggage.
These small loupes tend to get lost, thus I like the less expensive plastic versions. In the meantime I have also acquired a metal Jeweler's loupe with a magnification of 15 x. And if you want to spend more money and want more magnification (on a fleamarket tour or a watch fair) then you should probably look at all the Jeweler's variations.