There are two cheap plastic bushings that cause that play. Not a super fun job but its doable.
I see the problem though...the mircofiche doesnt show them separate on the GTX/GSX microfiche.
I will have to go out and check some parts, but I'm fairly sure they are the same bushings as the X-4 has. Heres the 'fiche
http://partsfinder.onlinemicrofiche...s/Seadoo_OEM/Seadoo_PWC.asp?Type=13&A=42&B=32
#68, 69 (which is obsolete)
Or...hunt down A UMI kit which has bearings.