I’ve stumbled across another maker of washboards. Cincinnati Washboards is, so the website informs us, the labor of love of three Argentine cousins: a musician, an engineer, and a designer. They build wavy-crimp boards designed to be played à l’américaine. Each has a call bell mounted on it. You can even get the “Big Farmer” style with a pre-rusted playing surface!
I trust that the prices they quote on the site are incorrect in some way:
Modern Washboarder Magazine 
Hi! I would like to clarify that prices are in “argentinian pesos” (1 U$S = 15,5 argentinian pesos).
Thanks for the clarification!
The symbol for Argentine peso is the $ sign.
Currently about 60 Arg$ to the US$.
Thanks!