Marksmen figures were sold in the 90s in bags of 18 figures with 3 of each pose for around 15 USD.. I've picked up a good number in bags or singly of the marching Union pose. Replicants makes them now but they are very expensive at around 18 USD of 6 figures.
The marching Union soldier is a good sturdy figure and correct marching pose. Plus, he can be converted with Armies In Plastic heads.
I have around 40 figures with makes enough to show some drill positions.