I keep some pump strapped to every bike inside the rear triangle by the seatpost - easy to get to once you're used to carrying it there. I prefer Sabre brand sprays about the size of a red bull can. There's also smaller keychain ones that have plastic holders that can be discreetly ducttaped to the seatstays and be in a swivelling quick release holder. Looks like a CO2 cartridge even among cyclists-