i used ultra-small binox for years but often even left them behind when i shouldn't have, so went to a monoc.
after trying different ones i carried the modern Zeiss 10x25B "Design Selection" model for a while (second from right in pix below) but even left that behind at times due to being just a tad too large.
it took a few years to find the one i really wanted: the much smaller & straight tapered long-discountined Zeiss 6x20B Classic.
after years of pocket carry, i've never had to leave this one behind.
here's a pix i just took of it:
Zeiss makes a bunch of newer models, and while they don't come cheap, they are worth every penny! because of the ultra-high optical quality, i can see detail you can't with much larger and more powerful optics.
http://www.zeiss.com/sports-optics/en_us/nature/monoculars.html#modelsin particular, i like the one close to what i carry, the Mono 6x18 T* (third from left, and re-shown below)