Thanks for all the pointers - very handy, and some of them compare very favourably, at least in terms of price, with many top models.
Reason for the question: there is a possibility, at present a slim one, that my single-legged status might double in the next few months, and although many bilateral (technical term for no legs at all) amps DO ride bikes, a decent trike looks like a far better option at my time of life.
Thanks again for the help.
Allen.