I usually keep this stuff in my Minox travel kit bag:
Light meter; I keep a Minox meter in very good working order as well as a CdS one (usually Lunasix 3 or Sixtar, both from Gossen, both well calibrated), or my Weston Master III with the new selenium cell, refurbished by Ian Partridge. When I am shooting some difficult to read scenes with an unmetered 35mm camera, I take my readings from one of these aforementioned meters. I take this opportunity to praise the not so acclaimed Vivitar Electronic 45 light meter, which is a very good tool, albeit of its so and so reviews I’ve read.
Film; mostly b&w, ranging from 25 to 400. Obviously it’s a matter of where you go, what season is it, things kike that. It’s always better to keep a few with you, even if you do not get to use them all. Better safe than sorry, I say. I also keep some color 100 or 400 just in case.
Flash: the electronic 8×11 Minox flash, and a bulb flash unit (either the Minox BC or the EMO BC), together with a box of AG1 bulbs. The EMO is pretty handy, for it can be used with old cameras too, if you take one along.
Battery: 1 x 5.6v fresh, a 15v for the BC flash unit, 1 x AA for the 8×11 flash, and 4 LR43 cells in an adapter.
Empties: 2 x plastic Minox film cases (the coffins, as someone called them). These are ideal for storing your shot film, if you do not reload your Minox cameras. Otherwise, you put the shot film in the case where you take the fresh film from, in case you reload.
9mm tape: I use the 3M brand, red tape. It’s resistant and almost the same width as the Minox film. Good if you need to re-tape the leader of the film in the take-up spool, if an incident occur. But any tape will do, really.
Pencil/notebook: simple stuff, small, for taking notes or writing on labels. A small black marker pen would be nice to have, it writes mostly on anything.
Small scissors: just in case you need to open the cassette (in dark) and cut or shorten the film. I actually have a small Swiss Army pocket knife, multitool. It has the basics for whatever I may need in an emergency.
Self-adhesive labels: I keep 10 or so in a small packet in my bag, for re-labelling the film, size 1cm x 5cm, white.
Tripod: the Minox one can be used, by I usually have with me a smaller one, Hama, with a release cable and a Minox tripod head, for those night shots or slow speed film shooting. I also throw in an LX tripod head.
All of the above occupy a small space in my bag, and they’re light to carry.