The Tehnolog plastic figures are marvelous to grimdark up. And cheap too! There is a large range, though i think the hard plastics are the preferred option (they also do soft plastic). They are produced by a toy company in Russia. There is a website, but i don’t think you can order direct from the company. They produce minis in a few different scales, including their fantasy battles range which is in 54mm. They also manufacture terrain and vehicles and mechs.
The figures themselves are one piece plastic and they are designed to stand without a base. So the pose of the minis is not that dynamic, and fairly similar across their range. It is an eclectic mix of minis they produce- from fantasy to historic to futuristic.