I do see the green ones occasionally in thrift stores. They're often a bit on the 80's side. I bought my boyfriend a red Lupin jacket when he wanted a green one, and he was a bit upset. I told him he could look for himself next time
He actually ended up cosplaying Nabeshin (Excel Saga, based on Lupin III), so it worked out. Photos in my gallery...
but yes, eBay is a great resource for things like this.
I love seeing Lupin cosplay. More Lupins!