Add CBN wheel to left side of T-8

[GbuserTX]

Hello! I thought it would be clever to add a CBN wheel to the left side of my T-8 in a coarser grit for grinding alongside a DF-250 diamond wheel on the right. Made sense to me since the CBN doesn't want a water bath.
Unfortunately, the 12mm arbor isn't long enough to mount the CBN wheel and none of the places I visit have a solution.
Anybody know of a way to make it work? Longer arbor? Arbor extension? Reference to actual suppliers would be greatly appreciated!