On Fri, 1 Jul 2011 08:15:55 +0100, "N_Cook" wrote:

Returning to plan A. What I think of as a lawnmower connector, 2 part outer
shell. Just space to mould in the existing US plug and fix in a third pin.
All demountable leaving the original cable and plug untouched, if so
required. Then either black nylon spiral wrap or heatshrink over the green
wire along the original cable. Satisfying the original brief but would be a
lot cheaper for him just having 2 core cable replaced with 3 core and 3 pin
plug, retained in the cab for any , unlikely, future USA based user.

Since the owner wants the amp to be at least retrievable then why not
un-solder the old cord, coil it uo, and store it inside the amp.
Re-wire witha grounded cord. Then if he ever wants to return the thing
to stock someone can remove the cord from inside the amp and solder
it back in place. Probably my suggestion will not please your customer
though, you must have already suggested this.
Eric