There is no US "issue" shoulder holster from that time period. However, officers were expected to purchase their own equipment, and once in the field a lot of non issue was seen, both officers and enlisted. Certainly, if conditions make one useful to you, then by all means use one.
The US army leggings from 1884 on lace up just like the ww2 ones. The only real difference is the strap under the shoe. Leather for Pre WW1, web for post. The Marines had some different ones with all eyelets due to a contractor dispute over the "hooks". Ned could tell you about those.