If you scroll down the page to the part #s, and click on a part number, then scroll down the result, there should be a list of the models that part will fit.
All Years HS80K1 WAS SNOW BLOWER, JPN Honda Snowblower AUGER Diagram and Parts
Just using the first part that comes up, 23375-732-000, the distance collar, the list shows it fits the HS50, HS55, HS70 and HS80. Since some of the parts are so universally used, this could be why the auger section isn't shown for the HS55.
23375-732-000 HONDA COLLAR, DISTANCE (Honda Code 1315274) $5.25
Unfortunately, there's a few parts that are listed as obsolete, and it looks like the auger shaft is one of those that is.
If you take that same number, 23375-732-000, and google it as Honda 23375-732-000, you'll come up with a lot of potential sources for it.
honda 23375-732-000 - Google Search
It looks like you're best bet would be to contact a number of Honda dealers to see if they have access to what you're looking for.
Honda Power Equipment - Find a dealer
I can say from experience with older Honda lawn mowers, that if the part isn't shown on the boats.net site, then it most likely isn't available.