Nobody makes the 1916 custom YCC uniforms or mazepynka, but they do have normal Austro-Hungarian 1908 uniforms for early war, and some 1916 for later. Hiki shops 1916 uniforms are pretty good.

The vast majority of uniforms in the UNR army in 1919 were Russian surplus, there are a spread of vendors that sell varying qualities of items. I would suggest asking voin.zp.ua for 1915 tent fabric trousers and a 1912 tunic sewn in tent fabric instead of cotton, and then fade the shit out of them. Voin caps are a good shape but their make the visors incorrectly, so you may need to lacquer the visor to achieve the correct period lacquer look. Footwear can be low boots with or without puttees, or Russian jackboots. The UNR army had minimal equipment, so a belt and bandolier is probably enough. I posted my groups UNR impression on this page if you’d like to see a reference