As many have said many times before. Stick with the major name brands. Gemeinhardt, Yamaha, Armstrong, Emerson, maybe an old Bundy or Artley.
It is better to buy an instrument that can be fixed instead of a throw away piccolo that may break in a month or may last for years. You never know what kind of luck you will have.
Just out of curiosity, since I never did marching band with flute/pic and played clarinet in those days, is there a preference when marching with metal versus plastic?
I would not make much of a distinction in metal vs plastic. Some may say that metal is louder because of the bore shape. Some may prefer a metal emb plate. I'd say that it's all in what you are used to after you practice the beast.
I agree with buying an instrument with a known name and from a source that has some sort of guarantee. I'm not a piccolo playing fan, even with marching...LOL! When I had the fortune of 1st chair, my 2nds always liked me because I would happily give them the piccolo parts with the solos Fortunately, I moved during high school to a school that focused on the concert season and didn't march, so I got a reprieve from my "can't walk and chew gum at the same time" coordination (or lack thereof...). I greatly admire anyone who can play a good pic. (especially if they are marching at the same time). Good luck with your search for the right instrument.