You sould be able to get load resistors local to you, try motor bike shops that sell LED indicators or fleebay (but that would take time), there must be other places to get the flasher unit from but beware of the ones for leds only, this was a unit that I found when looking for a unit for a local Zero owner, here up norf and it works great, just unplug the old unit plug in the new one.
Give them a call they may stick one in the post for next day delivery for a couple of Quid, and it only takes seconds to change, also in the future you can change the fronts to LED's and not fit load resistors.
HTH
Steve