I saw this weird portable cooler at Syntrend today. It’s a neck band looking thing that has some fans. When turned on the inside edge (part touching your neck) gets COLD, while it blows that same cool air into your collar.
I don’t remember what it’s called but it was quite expensive.
I’ve always had a thought to find a small compressor and build a small refrigeration loop that fits in a backpack, and runs on batteries, that would blow cold air into your clothing so that you feel cool no matter where you go (could be useful doing HVAC work or working in places where cooling is impractical).