Who decides what uniform an Indian country law enforcement officer can wear and who pays for it?
Primary source
Verbatim text below is from the Electronic Code of Federal Regulations (eCFR), a public-domain U.S. government work. Always verify the current version with the eCFR before relying on it for any legal matter.
Full Text
Each local law enforcement program must establish its own uniform requirements for patrol and detention personnel. Uniformed BIA police officers may be paid an annual uniform allowance not to exceed $400. Local programs may provide uniforms and related equipment to officers in lieu of this payment. All law enforcement officers must also have their official identification on their person at all times when performing law enforcement duties. Uniforms, when worn, will be plainly distinguishable from the uniforms of any non-law enforcement personnel working on the reservation.
This is legal information, not legal advice. Laws vary by jurisdiction and change frequently. Always verify current law with official sources and consult a licensed attorney in your jurisdiction for advice on your specific situation.