Yamaha DTXpress/DTXplorer/DTXtreme

I was told yesterday that in order to make my Roland FD-7 pedal work 
with my Yamaha DTXpress module I needed to buy a part from 
drumbalaya.com because the polarity on the Yamaha and Roland parts 
are different. The only problem is that it seems liek I may not be 
able to get it shipped to Canada in which case, I'm stuck but if it 
is only a mtter of polarity, could I simply open up a 1/4 inch cable 
and soder the wires backwards (negative to positive and positive to 
negative) Or does anyone know how to make a reversed polarity cable? 
If so, would I use stereo or mono?