Let's face it: Spirit was all set to be a horrible depiction of a Native American and in the cartoon, that's kind of what he was. Thankfully, in the comics Larry Hama was able to portray him as someone deeply connected to his native heritage without sounding too much like Tonto.
When I went looking for a miniature for Spirit, I ran into some similar problems. Most Native American gaming miniatures are of the 'Savage Indian" type. Not what I wanted for Spirit.
Thankfully, the Star Wars Miniature Jariah Syn already had most of the look I needed. I added the headband and shirt details with green stuff, and removed the weird throwing star. Too bad I don't have a little eagle to perch on his arm.