I do not know of a clicky tailcap that will fit the L2. If one can be found, it will function on high only. The two level output is usually the reason you would buy the L2 in the first place.
Someone might know of a non SF tailcap that would fit.
The L2 with a clicky would basically be an L4. If that's what you'd like, sell your L2 here on BST and buy an L4. You could probably find someone to trade you as another option.