Does anyone know where I can get a katana 600 shock from? All I can find is the spring

Are you looking for the linkage off a katana 600 along with the shock? Most people leave their stock GS500 linkage and just replace the shock itself.

If this is the part you are finding, it's correct. Not the best example for lowest price, though.
http://www.ebay.com/itm/Katana-GSX-600-750-GSX600-GSX750-Rear-Shock-Suspension-Spring-/120915119836?pt=Motorcycles_Parts_Accessories&hash=item1c271a4edc&vxp=mtr#ht_1131wt_1344

On the other hand, if you're looking for the shock plus linkage, they are out there, too.
http://www.ebay.com/itm/97-Suzuki-Katana-GSX-600-F-rear-shock-w-linkage-/200788953570?pt=Motorcycles_Parts_Accessories&hash=item2ebff449e2&vxp=mtr#ht_1988wt_1110

Or maybe you're looking for a Katana 750 shock that also has the reservoir.
http://www.ebay.com/itm/258-98-07-SUZUKI-GSX-600-750-KATANA-REAR-SHOCK-/221051100905?pt=Motorcycles_Parts_Accessories&hash=item3377ac1ee9&vxp=mtr#ht_2923wt_1110


To put it differently, ebay is a good place to start.

Awsome thanks for that should I bother with the linkage? What would be best for a 95kg rider?

I wouldn't bother with the linkage. The stock linkage should work just fine. Check out the wiki for details, as well as some of the options people have used/made work.

If you do a search for katana shock on the forum, I think you will find some settings that others have used. I still have the stock shock, myself, but I'm seriously considering swapping for a katana 600. (I'm quite a bit heavier than you at about 295 lbs, though, and I have the stock shock set to almost the stiffest setting just to manage the sag.)

The general consensus around here that the first suspension modification you should make would be to look at stiffer fork springs to better manage the front plunging during heavy braking. For someone your weight, I would guess that the stock shock could just be dialed up a bit if you feel it sags too much when you are just sitting on the bike.

I have found both a gsx600 rear spring and rim off a 95 model but have heard some year models don't work do you know weather these bolt on or not?