Hardshell Trunk:
Here are some pictures of a hard shell trunk I made for my all-weather commuter out of a industrial dual compartment mop bucket. I bought this bucket at Lowes for $12 but I have also seen it in the McMaster-Carr catalog for the same price.
I removed that handle and cut the bucket in half, each half had a
3/4" flange that I pop-riveted to connecting plates that were the same width as the Blackburn
rack on the bike.

The top is a piece of a polyethylene foam boogie board I picked up
at the dump. I made a cover for it out of water-proof nylon and added a skirt with a
length of shock cord sewn into the hem.

Pieces of shallow aluminum "c" channel front and back stiffen the
bucket. Above right you can seen the hole for the Vista Light switch. I filed off
two of the Vista Light's mounting bumps so it would sit at the right angle when screwed to the
bucket. I also seated the Vista Light in a bed of Silicone seal before I screwed it down
to ensure a watertight fit.
The piece of stainless steel at the front hooks over the front of the Blackburn rack. The middle portion of the "bridge" between the bucket halves is black polyethylene and the rear portion is aluminum. Everything is pop-riveted together and liberal amount of G.E. Silicone II Window and Door Sealant were used throughout.

The aluminum block in the center hooks over one of the cross bars
of the rack. The whole trunk comes off with a twist of the knob on the top.
I've been riding with "The Bucket" for about a week now and it is
working very well. I did add some foam liners to the bottom of each bucket to prevent my
keys and other hard bits from rattling over bumpy roads.