Frame Sliders from T-Rex Racing: http://t-rex-racing.com/catalog.php?item=253
Frame Sliders from R&G Racing for GS500E: http://www.rg-racing.com/browsebike/Suzuki/GS500_Unfaired/All_Years/CP0157BL/
Frame Sliders from R&G Racing for GS500F: http://www.rg-racing.com/browsebike/Suzuki/GS500_FullyFaired/All_Years/CP0158BL/
Frame Sliders from forum member reload: http://gstwins.com/gsboard/index.php?topic=67940.0
Frame Sliders from Wild Hair Accessories: http://www.whaccessories.com/Suzuki-Sliders-GS-500-E-88.htm
The GS500F does not have any holes in the fairing to allow frame sliders mounted to the frame to pass through. Therefore, if you want to keep your fairings intact, the only option for frame sliders is to mount them to the bolts that hold the fairings on. However, in the event of a crash, this will put enormous stress on the attachment brackets, and will most likely damage them. For low-speed or zero-speed drops, however, they should be fine.
Fairing bracket:(Notice how flimsy these brackets are! They don't stand up to much.)
It is vastly preferable to mount the frame sliders to the engine mounting bolts, as other bikes do. However, this will require you to cut a small hole in the fairing. This, if done carefully and neatly, looks fine and does not detract aesthetically from the bike.
Here are sliders mounted to the engine mounts:
R&G sliders attached with fairings