Gazelle type adjustable stem for MTB?

[dzh]

I am planning my new build, was wondering if there are any sort of adapters or solutions to get this easily adjustable steering wheel:

https://www.youtube.com/watch?v=awag66wjX4k

Most(?) MTBs come with top-cap stems, however this Gazelle solution is whatever (sorry, don't know terminology) type.

I know I can get something like this, but it's not elegant - it does not go backwards.

My build focuses on comfortable ride, rather than aerodynamics. However I'm choosing MTB frame for brakes and general sturdiness.

Any ideas or suggestions?

Edit: just found this, seems like it could work, now?

 

[d8veh]

You need a threaded steerer tube on your forks and a threaded headset to use a quill-type stem like that.

You could probably adapt a set of threadless forks by using spacers and a clamp without the stem fitted to adjusted the steering head bearings. Once the clamp is tightened, you can remove the cap, knock the star nut right down through the steerer tube, and then insert your adjustable quill stem. There's two sizes 1" and 1 1/8" most MTBs except the cheapo ones use the latter.

 

[LewTwo]

What about just threading the top of the 'threadless" steerer tube to make it a "threaded steerer". Of course 1 inch and 1-1/8 inch dies are not cheap but most local bike shops should be able to do it for a reasonable fee. Am I missing something obvious? There are a number of shims available to go from 1-1/8 inch down to 1 inch.

Fair warning for anyone thinking about buying a threading die: Some of these size dies come in 55mm and 2 inch outside diameters .... they are NOT the same. A 55 mm die wil NOT fit in a 2 inch die holder. ... and yes I now have both size die holders