I've looked around and can't seem to find anything at a reasonable price with shipping to Canada. I've been using my backpack to bring my lunch bag to work but would rather just mount it on the bike.
Any help would really be appreciated.
In Canada are there any distributors of Givi, Shad, Hepco & Becker, Ventura or Renntec?
If so, they should be able to order the GS500 specific racks for you even if they don't show the racks on their website. You will probably have to call them on the phone with the model # from the rack manufactuer's website. Be ready to wait awhile for the rack. Some stuff I've ordered from Hepco & Becker for less commonly accessorized bikes (like the GS500) is made to order in Germany so it can take up to 8 weeks to arrive. If you had a more commonly accessorized bike like a Vstrom or BMW R1200GS they would have the racks pre-made and in stock.
Looks like Motostarz out of Vancouver sells Hepco & Becker. H&B has rear and side racks for the E and F model GS500s. Givi and Shad might be newer style bodywork only. Ventura and Renntec are rear rack only but should have options for '89 - '00 and '01+ style GS500s. Note that Ventura only sells cloth bags for their racks and Renntec sells no bags for their rack. All the others sell purpose built locking hard cases that are interface with the brand specific racks.
There are cargo lugs under the seat. Just grab yourself some occy straps and carry your lunch box pillion.