Welcome to the Bunnings Workshop community. It's wonderful to have you join us, and thank you for sharing your question about pebblecrete.
I suggest having a look at this discussion - Re-surfacing pebblecrete by @JRRed. The product that was recommended to resurface pebblecrete was called Megatreat. However, did you want to resurface the pebblecrete with cement? Before the advent of pebblecrete kits, the traditional method was to mix the pebble create with the mortar and spread it over the surface. The top was then either hosed off or wiped off with a large heavy sponge soaked in water to reveal the pebble tops.
Unfortunately, this is not a service the store offers, I suggest posting your job on either Airtasker or Hipages. My number one recommendation is to put in as much detail as possible so that you will get quotes quickly.
Please keep us updated with your progress, we look forward to seeing your pebblecrete resurfaced.