They are custom made by McGizmo.
The "Aleph System" is a modular flashlight-Lego system based on the SF E-Series and is fully compatible with all E-Series compatible lights.
Alephs or Aleph parts for DIY are sold in the Sandwich Shoppe (see forum) and can be ordered from some members: Darell, tylerdurden, Chop, kj and JollyRoger. McGizmo doesn't sell Aleph products any longer.
If you want to know more, visit the McGizmo sub-forum and have a look at the sticky threads where you will find all the answers to your remaining questions.
bernie