Since we usually travel two-up our possibilities are limited. However I managed to fit two of these on the back of my bike, next to the tent:
Pretty comfortable yet sometimes the ground seems more comfortable (rarely though), but they keep us dry and sometimes can be quite useful. Dirt cheap (5€ each) so in case of loss, damage, theft, etc. not a big loss.
"Life is not a journey to the grave with the intention of arriving safely in one pretty and well preserved piece, but to skid across the line broadside, thoroughly used up, worn out, leaking oil, shouting GERONIMO!"