Weird. I have more Further Austria coins that I know what to do with (most of them in awful condition, mind you), and do not think Duchy of Warsaw is all that rare either.
Unfortunately, I am unable to legally send any of those to you, because without documentation to the contrary they count as Russian cultural property (I'm willing to sell you some if you visit Moscow, at which point any further customs problems, if any end up occurring, would be on you).
If you can visit Russia, might as well get some Crimean coins (not that hard to get a hold of in Moscow, just expensive and/or hard to attribute; not sure about Saint-Petersburg, but probably similar).
Might not be specifically kopeks though

18th century Crimean denominations are tricky as ch*rp anyway.
There should be plenty of German States coins even in your country, as metal detecting finds. Bishoprics is trickier, but a few of them were close enough that it is possible you'd get some anyway.
Swiss cantons is pretty much luck of the draw. I didn't see any of those under $50-ish in Moscow for years, then found a few in close succession in the $10-15 range (didn't buy any, not enough money).
According to coins-numismat.ru (formerly coins.numizmat.net), the big coin shop in your city is at Sammonkatu, 14-16 (wherever that is).
There is supposed to be a weekend flea market in Helsinki, which might be a better choice for cheap MD finds (which is the most likely place you'd find anything from the German bishoprics).
No comment on Kievan Rus except "if you have the money, watch the big-name auctions, they have those occasionally".
Same for countermarked cut coins, except that those don't cost
that much money.