I think GSR were talking about them (under the ancien regime) but don't know if anything came of it. The problem is always going to be that 4 pipe join.
That also gives links to the parts you want, as well as sizes.
ASH sell hoses at very reasonable prices, and they also sell air filters. I've got the measurements i used when i made my induction kit up if you want them, so you can build it yourself, in whatever colour.