If you want to have a go at making a body for a Generation type mouthpiece, get yourself down to your local Wilkinson’s and check out their small Devils pitchforks. The bore of the black plastic handle is just the right diameter to take a D top.
You get a foot and a half for 35p.
It’s a bit flimsy so I cut a section length ways and glued it round the outside of the rest of the piece.
The plastic drills and files well and I made a whistle in 1 hour.