The military forces of the Princely States (or Native States) formed a reserve for the Indian Army, wore Indian Army uniforms and used British equipment. So at a pinch, you could just use some sharp-looking sepoys of your period, and try your best to paint them up as colourful dress uniforms, rather than drab khaki (and you could go to town inventing your own if it is a fictional Princely State).
However, the uniforms of troops kept for ceremonial purposes tended to be a bit more lavish. I'm not aware of too much out there that completely fits the bill, but the idea of using figures from a slightly earlier period for their fancier uniforms, or Afghans or Sikhs etc. is not a bad one.