I’ve tried using a “Respro” face mask, but I can’t get it to fit with my riding spectacles. The “bandit” bandana works well, but the internal carbon-impregnated cloth just collapses after a while.

Can anybody recommend an alternative? 🙂

Anything that’s actually effective at filtering pollutants is likely to have a rubber seal and a canister or two hanging off the front, as well as insufficient airflow for something like cycling. A layer of charcoal cloth badly fitted to your face doesn’t do much at all when it comes to smaller pollutants, except maybe act as a placebo.