If you are not travelling to gigs in a car, and you don't have guaranteed access to a PA system, you'll have to go light, small and powerful enough to be effective.
500 watt D class amps are between 4 and 7 lbs and the smallest, lightest and loudest cab I know of is one of the Barefaced 112 cabs.
Put it on a trolley and you're in business.