I have been searching for several years, through speaking with other truck enthusiasts, literature, other forums, etc. and have come to the conclusion that GM (chevy or GMC) did not make covers to fit the storage compartment under the drivers seat for suburbans. I do have a cover thats fits the panel truck tool boxes (somewhere along the lines of 9.5" x 16"), which comes up short of the overall length of the suburban storage hole.
I would be very interested to hear from anyone that has found information that differs from what I have come across.