Do I presume that you do not do conversions? According to my sources, any figure with a German Helmet or field cap can be used for Finns. In my own Finnish army I have Revell WWI Germans, Airfix WWII Germans, Airfix German Mountain Troops and Revell Siberians. Just a paint job conversion for these.
Ceaser has WWII Chinese slated for release, but you can basically use any American or Japanese figure. Remember Chang was supplied by the Americans and the Chinese were also put a lot of captured equipment to thier own use.
If they look close enough to them on the table, I plan to press these Romanians into the Dutch Army while waiting for the Ceaser release.