there are/were some stock looking pipes for caminos by fast arrow, tecno, and a few other brands. I'm assuming some are better than stock, since they're described as tuning auspuff vs standard.
hard to be sure though with google translate, one description said "not throttled" , restricted I guess? did euro pa50s have the 20 and 30 mph pipes like we got in 78-79, anyone know?
if you search here you will find more info, there's a small english forum and more info that you will have to translate.
if you do find one, i'm sure shipping won't be cheap, but since you said money is no object...