I found three near-new Underwater Kinetics model 518 cases, complete with foam linings, at a local pawn shop today. I got them all for $48.00 plus tax. I am not usually very lucky at finding deals so I just had to brag a little about this. They are an older model but are still available online.
Internal Dimensions: 17.8 L x 12.8 W x 5.1 D in
Lid Depth: 1.8 in
External Dimensions: 18.5 L x 14.6 W x 5.9 D in
Weight (empty): 7.1 lbs
Submersion Test Depth: 1 meter
Materials: Ultra high impact ABS, stainless steel hinge pins, silicone rubber o-ring
Internal Dimensions: 17.8 L x 12.8 W x 5.1 D in
Lid Depth: 1.8 in
External Dimensions: 18.5 L x 14.6 W x 5.9 D in
Weight (empty): 7.1 lbs
Submersion Test Depth: 1 meter
Materials: Ultra high impact ABS, stainless steel hinge pins, silicone rubber o-ring