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That uniform looks like the Shrine Band Uniform we used to wear about 25 years ago. You might check with your local Shrine for a stash of old uniforms or try a costume shop in the larger cities.

Schlep ..... two places to look .... Ebay... duh .. and also a few years back I wanted a band uniform to wear as a Hallowen costume only I wanted a real one. It seems to be there are a couple of places that take in old band uniforms ,like when band change from one style to another, and then sell them. I remeber finding a place that had all sorts and sizes and they were cheap too ! Google.... it's your best friend .

Magnolias Used Band Uniforms : http://magnoliasusedbanduniforms.com/BandUniforms.aspx" target="_blank

Don't bother, nothing you find will fit you.