I have always wondered at the lengths people go to avoid wearing a helmet..... when they actually have one, be it ever so crappy, on board!
Carry in the hand
Carry in the same hand as the cigarette, and/or phone,
Hang it off the handlebar, or a hook, or almost anywhere,
Stuff it under the seat, if it's possible
Give it to the passenger/s to carry (along with their own if any)
Stuff your through and wear it like an armband
The easiest and most comfortable way to carry the damn thing is, guess what? On your head. (Correctly, with the strap fastened, not with your eyes below the chin guard, if it's a full-face model!).
Then there's the camouflage. Make it look like something else.
Bunny Rabbit ears
Alien antennae (aka cable ties or tie wraps)
US army helmet
Nazi helmet
Skinhead/Hells Angel skull cap
Jockeys hard hat
Contractors hard hat
Some of these are not safe, and any may invalidate any financial claims arising from an incident.
Why not wear the thing openly, and advertise the fact that as a rational being, you accept that hitting things with an unprotected head carries the risk of serious and lasting damage to your life!