hifi engine

AKAI GX 4000D speed sleeve

I just got an Akai GX 4000d and noticed that the speed sleeve is missing.
Does anyone have the exact quotas of the small tube that fits on the driving axe?
I measured this axe and noticed a 3,9 mm. The big diameter is somewhere around 8 mm but I need the EXACT mm size, as well as the length is about ... 13 mm.
I will do it by myself using Al hard alloy, as I cannot afford to pay 60 $ in order to fix my 100 $ RTR player. Thank you for your help.