Yes you will be able to get brake booster parts at auto stores. You can try with online stores that have several varieties to choose from. For example,
Car Junky is a website that sells brake booster spare parts at discounted rates.
Race Pages is another website where you will be able to find brake spare parts that you want.
Another great site is the Auto Parts Warehouse where you will get really great deals.
If you don’t want to order goods online, we suggest that you check your local Yellow Pages to find the stores that do have brake spare parts.