I had some trouble sourcing replacement air pipes for my 175HS. I ended up making my own from stainless tube and then polishing to a mirror finish.
I bought a 500mm length of stainless 45mm (1.75") diameter stainless tube and cut it into 86mm lengths. I then polished them using a mop and three grades of grit. I left two round and squeezed two in the vice to make them oval. Well impressed with the result and they work out at around £3.00 ($4.00) each, result.