Here is the dimension of the main jet:
Diameters: Fine-thread: M5, Head: 6mm
thread length: approx. 3.5mm, length over all 9mm, head hight: 4mm
Length: over all 9mm
Just have a look also to 4-Stroke Suzuki-Marine engines with Carbs. They should also have Mikuni Carbs. It seems that also jets of Keihin Carbs could fit....(even if they are from 2-stroke engines(!)... They have all the same nozzle-producer. Best way is to compare with your stock jet at the shop!
btw.: I am often in Slovenia and Croatia - my wife is a "koroske slovenske" (hope I spelled it right.
.) and she speaks slovenske as second native language. So, if you will send a private mail we would visite you sometimes in sommer (and vice versa to you...)