It will fit your 2003 model fine and indeed it fits all 2000-2003 bikes. They are becoming rare (or more specifically the FZS600 fitting kit is) so they command decent money. Each indicator alone costs £30 each new.... but try not to go beyond £100 maximum
The rack won't fit 1998/99 bikes, but it can be made to do so.
The issue is the pillion footpeg hangers which the rack attaches to. The earliest bikes had the hangers mounted with the pillion footpegs quite high up. From 2000 onwards, the hangers were changed to allow the pillion pegs to be mounted lower and the Wingrack attaches to these revised hangers. The most obvious way to tell what hangers you have is the footpegs - 1998/99 bikes have alloy footrests whereas from 2000 onwards the rear footrests have a rubber tread layer added to them.
If you do buy it & fit 3 full-size cases, the pillion has very little room for their feet, but that's another story....