Convoy S2+ Extension Tube?

I am looking for an extension tube for my Convoy S2+ to build a current measurement adapter. Has anybody tested if one of the available 18650 extension tubes (C8, L4 or Non-Convoy) fits?
D80 (diameter) and BLF A6 (pitch) do not work.

(If you want to help - please do not put a second battery in :nerd_face: )

I bought all the smallest diameter extension tubes I could find and the smallest one fits the Jax Mini C8 but way too big for the S2+.

gearbest sells the convoy with it as an option. certainly they can get you one….

http://www.gearbest.com/led-flashlights/pp_299059.html

Very nice light BTW. I wish it was driven a little harder…

Thanks, but the L2 is a 26650 light. The tube does not fit the S2+.