True, I did this years and years ago when the CES was in Chicago and the"outlaw" exhibits were in the Bismarck Hotel. I just had a little mos-fet in a small Budd Box in my briefcase, complete with input and output cables.
I did talk a few exhibitors to try it out, always with pretty astonishing results. I stayed away from the big name exhibitors, but there were many "start up" speaker builders there that would have liked to have kept and use the briefcase amp for the show. Unfortunately I could not do that as it was an unfinished prototype. But it sure was fun.
Regards,
Frank