Same. Bungee to the back seat. Could be useful to carry the helmet when off the bike tho…

Could you recommend a specific pair of bungees please?

I have a set that have a ring in the middle, then 8 hooks coming off that. It’s like this:

I think I nicked it from my Dad. No idea where he got it. Maybe Halfords?

Oxford used to make a bungee ‘net’. Have carried helmet once or twice with it. But put the helmet in its bag first to avoid scratching

thank you both. The bungee net looks like a slightly more comfortable solution for the bike. 

I made mine with
36" (92CM) Cargo Strap Bungee Cord with Carabiner. Motorcycle, Motorbike or Roof Rack Cargo Net Tie Down.

And put some heatsrink around the clips i  Wise
Looks like a cock ring to me...

I like these, used them for a while

Too small for that.  Wise
Looks like a cock ring to me...

kinda off topic:
i have a 360reflect jacket that i wear over my gortex waterproofs, so dont care about how waterproof it is..
i have seen a marked improvement of cars being aware of me!
I've emailed them as I reckon there's a market for Proviz motorcycle over jackets. The ones worn by cyclists are excellent - if they could design one for biker use (as I've never quite got why winter jackets are predominantly black, just the season when you need to be seen) the market would be good.

I use these for carrying a helmet

Proviz used to sell motorbikers hi viz stuff but for some unknown reason stopped about two years ago

Don't want to sound too negative, but I would never drive with a helm in my backpack. If a crash were to happen I wouldn't want to land on a helmet with my back, I could well not get up anymore. CBR500R commuter
Me neither. I prefer helmet on my head while riding, but once bike is parked it's easier to carry it in backpack :)