Continuation War Finns, the proper, manly, way.
Take a box of PSC plastic Russians. Warlord will do at a pinch but you will end up with less useable figures.
Beg, borrow or steal some of the old Wargames Factory Germans for head transplants. Other useful items of kit can be found in various Voldemort plastic boxes.
Scribe the front of the PSC Russians tunic, to give the appearance of a conventional full length tunic. You can get a pretty good approximation of the Finnish summer tunic this way.
Paint appropriately.
They won't be perfect, unless you really want to faff about carving off equipment but I'll wager they will look closer to the mark than the misshapen dwarf children that Warlord pass off as Finns and they will match other ranges better height wise. Given the Finns used the DP LMG at twice the rate that they used their own domestic weapon, you can happily use them as is.