Don't think the Helios trigger is the same part. RC Disco have/had some great deals on KO stock that came across from the old distributor - hence why I'm now running a 40meg Helios! Be worth speaking to Greg as he may have a box of bits that weren't worth putting on the web site if he only had 1 of them at that sort of money.
They still have EX-1s with 2.4G modules, or Helios with 40meg, but no handsets only left, to my knowledge. Since the part is only $3 it seems a bit extreme to replace the handset
I know someone that ordered an OS Speed from that Hong Kong based shop - took a while to arrive, but if Greg doesn't have the part it's got to be the best value option