Electric assist tricycle? Need mobility solution.

Please help:

I have a friend who suffered a stroke and now has quite limited mobility. He is still super independant and likes to go to the Islands to putter around his boat. He is able to get around with a cane on his own, but the problem is trying to cart his gear... he still has balance issues and has already wiped out pretty badly trying to cart things around with a bundle-buggy.

He is interested in getting an adult cargo trike (or quad) of some kind but worries that he won't have enough strength to pedal it forward once loaded. Does anyone know if there are any electric assist adapters that might work for a tricycle?

Any other ideas for (stable) self-propelled mobility?

Thanks!