Early drum-brake Minis had a single wheel cylinder on each front backing plate. This cylinder is finally available as a reproduction at a modest cost. This wheel cylinder is 15/16" bore, and if fitting only one, you must check the bore diameter of the one you are retaining to ensure it is the same as the new one. If not, you should replace both front cylinders to make sure critical front braking performance is balanced.
See also OEM version cylinders GWC0101.