Ray,

Eddy, Jazz and myself have all said the same thing, and any supply to the switch between 10 and 36 volts will work.

The only reason I'm being slightly pedantic and suggesting you do some basic voltage checks is to avoid any issues or disappointment. Chinese supplied products can vary in subtle ways especially stuff on ebay. That switch comes in 2 variants. One is truly just a switch to ground and that's what you need. The other version has an internal pull-up resistor to the +v supply and if it's that version then there is a chance you could damage the BOB if you don't have a resistor between switch and input. All I'm saying is do the electrical equivalent of 'measure twice, cut once' :)