www.oceanline.com.au/ - Never used them - but a mate of mine has had a couple of custom boards off them and has been happy with both the service and quality.
www.surfsailaustralia.com.au/contact - these guys are based in West Leederville and 'outsource' their repairs... but the bloke who owns it said he does a really good job. The repairer collects the boards from the shop each Saturday morning and delivers them back the following Saturday.
And also Katana in Osborne Park - Dave's on the forum mostly in the Short Board surfing section.
katanasurf.com/Others advertise on Gumtree...