IK 435: we don't know exactly about Kiev testrunning, but the very first 435 (IK 435.K1) was tested around the eastern block from 1985 and 1988, so it can be what you looking for. The bus now in Salgótarján.

Two another prototype in the sowiet area:

-IK 435.02 from 1995 in Minsk. It scrapped last year

-IK 435.P2 from 1990 in Tallin. Now in Angarsk.