Kumihimo Supplies: Your Best Source!
Banded Stainless Steel Magnetic Tube Clasp 4 & 7mm
(Click on above picture for a closer look)
This is a very elegant design. The stainless steel is strong, beautiful, and durable, and the black bands are a great design accent.
Another nice design touch: there is no visible joint, since one of the cords will glue into an insert (see the photograph below). So, the cord appears to disappear into both ends of the clasp, with no evident magnetic closure (it is all hidden inside). The visible clasp tube is a single piece.
About 19mm long with a 7mm hole/16mm long with a 4mm hole for your cords in each end.