Any small light meter would be fine. You should be able to pick up something like a second hand Sekonic cheaply. Or even something like a Weston Euromaster, or other good quality analogue meter. Alternatively, if you have a smart phone (iPhone or Android) there are light-metering apps you can download that will turn your phone into a lightmeter and save you carrying another gadget.

If you are shooting in daylight, you might not need a meter. Sunny-16 is pretty accurate if you are shooting black and white or colour print film.

http://en.wikipedia.org/wiki/Sunny_16_rule

Personally, if I'm not in very changeable/mixed lighting conditions, I'm quite happy just guesstimating the light using Sunny-16 plus a few ad-hoc corrections.