Both Reservoirs on my MC crumbled when I went to remove them (upgrading to 15/16).
I searched on this forum and others for a source of replacements with no avail. I did notice that Tilton had some remote reservoir inlets that apparently fit our MCs well enough, though I couldn't be sure these were the same size as the reservoirs they sell.
Well, I'm glad to say I didn’t spend $40 something for no reason, because they fit wonderfully, look great, and make it much easier for me to have two large reservoirs for my rear caliper conversion !
Here is a picture, and part numbers for everything you need, incase anybody else can benefit from this information:
Reservoir - $7.99 - PN:3558-MEDIUM
Filter - $4.49 - PN:3559-LARGE
Cap - $5.99 - PN:3564
Clamp - $1.99 - PN:3577
O-Ring - $1.49 - PN:3556
Got everything from Pegasus Racing. 15/16 MC is a refurbished unit from Oreilly.