The earliest I have had my cats done at was 12 weeks, but that was done in Truro at the Truro Vet Hospital. And I am pretty sure the vets at Central Nova and Fundy will do them early as well.
As for vets in the HRM area, you might want to try:
Fairview Animal Hospital - (902) 443-9385
Bedford Highway Vet Hospital - (902) 835-2323
Basinview Animal Hospital - (902) 835-8383
Fundy Vets, Shubenacadie - (902) 758-3180
These are the only ones I can think of beside Carnegy's which rottn already mentioned.
Good Luck!