As I was just looking for a marshrutka in Ukraine in noticed the tag: https://travel.stackexchange.com/questions/tagged/marshrutkas
It's a Russian word commonly used in all countries of the former Soviet Union with no equivalent in English. I would suggest to use the Russian plural (which is suitable for most Slavic languages) instead of a weird arbitrary English plural.
Marshrutki instead of Marshrutkas
Or if there is no agreement on that the singular should do it: Marshrutka