Anybody know of anything that will work to hold a full-faced helmet and is lockable? It could be a real cargo carrier, or just something from Sears or Home Depot or whatever.
Waterproof/resistant would be nice.
Maybe somebody's already found or rigged something.
It will be stored in a garage, this is just for those 2-3 hours I'm inside someplace generally well-trafficked like a bar or restaurant or theater. It doesn't need to survive extensive urban overnight usage. It's a college town so my biggest enemy is probably drunken bro's.
Here's what my rear frame looks like, for reference: