As a detail was broken, I created a reaplacement part. We lended a part to take measurements. As Vjatka is not an exact copy of Vespa scooter, there was no Vespa-origin replacement part available on ebay. So this part does not suit for Vespa.
Detail is intended to fit to Vjatka 150 from 1950's. Not tested yet, will be installed in near future. But result seemed to be "close enough" :)
Scooter Vyatka VP150 (Vjatka, Vespa copy) from 1950's, info from Wikipedia
Designed with SkechUp
Best to be printed when it is placed as on main picture.