Something like the picture here. I want to wear that, it'd rule. I cannot for the life of me find a sports coat that isn't navy / black / blue / gray / dark green at best.
I've been to second hand stores, I've scoured the internet. My options are 500€ designer shit, which, no, not for a trial run and probably not ever, or polyester stuff from china that is gonna ensure I look like a melted candle wearing it and is probably made to fit for like an asians person frame not my golem ass
Where, I ask, where!
I'd look around for men's fashion forums or subs specific to your region. Summer weight jackets for more casual wear at least back in the day, used to come in more colors. These days though it seems like they've been out of fashion for so many decades it's hard to find them even in second hand shops.
Whatever you end up finding it's often worth taking it to a tailor to have it adjusted to fit better. A few alterations to the fit of a jacket can make it look dramatically better.
Thanks, but also, dangit!
Don't despair. Most places seem to have active men's fashion subcultures and in my experience, aside from some jerks, folks are happy to help new enthusiasts find their way around the local terrain.
I'd know where to find one but it'll be a trip