I reenact Soviet GPW as well! Some officers use Soviet Boots for at least basic approval. They don't fit my calves or I would've considered going that way. When I ordered my black staff officer uniform from Cosplaysky their jodhpurs were misshapen. I patterned better pants from my M43 pants, they have much better shaped flairs. I would try to get approval with your sagopai boots definitely, and if you sew, those NKVD trousers wouldn't be bad to base a pattern off of. Good luck comrade!