I don't know where to start:
First off, it's a proprietary part that must be bought through HM, all other comments on an alternate source aren't helping.
There is a lesson here on proprietary parts, if you don't want to buy proprietary parts, don't buy a machine that uses proprietary parts.
Bawb seems to have ingnored the horsepower differential of a 47 and 45, and the madatory plumbing of horizontal or Vertical ports based apon machine design...but anyways, this thread is about his HM spec 4007 blower...how did we get off on a 45 blower rant?
On Stevie's pump comment, I'll bet it was a case of "discount purchase" more than screwing the little guy, bet you a dollar to a doughnut, those japanese pumps were cheaper, and they bought a BOAT load.
On the Who gets the gravy, I would say everyone involved in the chain, why carry HM if you can't make money off the sale of the machine, the service, and the parts? Might as well build your own, it is a for profit business, I feel bad for ya gettin' the short end of the shaft. which btw, you should get a decent core charge for your old blower, they are just gonna put a new Lobe/shaft in it, and new seals, but they have priced the parts to discourage rebuilding them (more proprietary stuff).
As a final note, you don't hear about belt drive machines snapping blower shafts, consider that in your future planning.