barrels can be bought separately very easily.. people customize split wheels all the time.. making them is a problem im sure theyre a significant industrial process involved, i assume theyre flow formed. (they are check this link for ALOT of technical information - http://www.imagewheels.co.uk/pages/techincal_info.html).
as for machine shops.. Im sure there are hundred of people capable..
have faith in your ustads in the markets, they can surprise you more often than not.
Its doable. For sure. (only if you have your own barrels.)
You would have to have a very stable hand at cutting, using a very strong gas torch (using the correct mixture for aluminium) you can mount the existing wheel in a lathe and rotate it at the slowest speed while holding the torch in place at a pre determined point, ideally using a jig/fixture.
The better your prep the less chance of an imbalance. Similarly the rim will have to be marked perfectly and drilled perfectly. You could have the center once cut, 3D modeled (CAD designing) and the holes can be added to the design on a base circle with the correct PCD, similarly the design can incorporate the smoothness and roundness of the edges and you can approach small vendor engineering companies equipped with CNC machines to do it for you. (look up the Pakistan automotive parts manufacturers lists)
It would take some convincing to get them too, and would cost quite a bit.
But the question was doable.. thats how i would do it.
