I've often thought that a cylinder opposite my bike's muffler would make a great place for a cargo or tool holder.
Inspired by a portion of this other Pashnit thread, here's my execution of that idea.
Oggi brand stainless steel toilet plunger, model 7141 (plunger discarded) with its holder can: $20 online from BBQGuys.com.
Overall view of finished installation on my F800GS. Those are t-bolt hose clamps, a wonderful invention.
This method leaves a screw head inside the can, but it's smooth, anyway. Those are soft black rubber washers to keep knobs from loosening.
Looking down on rear mount. Rubber lined P-clips with 10-32 steel hardware. Thought I'd need a horizontal strut, but the geometry of this mounting is quite solid side-to-side, so that may not be necessary. I'll keep that possibility in reserve.
Front mount. It sort of evolved, and I wasn't happy with it half way through, but it worked out OK, so I'll leave it. That's 1/8" black rubber sheet (from hardware store) for P-clip shims, same material as glued in for lid gasket
For what it's worth...