Grumps, Bike Bug at North Sydney (JJjjuuust north of the coathanger) stock sidi’s and is where I bought mine, at quite a good price. There’s a slight chance they stock Giro’s but can’t be 100% sure.
I bought my Sidi’s from Clarence St. Having a weird foot shape I needed to try on several pairs of different brands and sizes so Clarence St (the street, not the shop) on a Sunday was a good place to start. Several shops there with lots to try.
The Giant store on Clarence St have Sidi’s as well.