For my new Shimano M780 based gear I need a pull down (or bottom pull) front derailleur with a 28.6mm clamp for a 3x10 without direct mount. All the derailleur I have checked do not have a 28.6mm clamp. Are there not produced anymore? And if so, what would be the solution?
You can buy a braze on derailleur of the type you need and get a Braze on to 28.6 adapter. Alternately, you can get a derailleur with a larger size and get a shim. Either will be perfectly functional. Very few Mountain Bikes have 28.6 downtubes anymore so the likelihood of finding a 28.6 seems pretty low.