Substitute for allspice berries?!
also called whole pimento, asda sell it
Allspice would be better as it may be difficult to get the balance right. You should be able get allspice berries,in most major supermarkets (I am assuming that you live in GB) or in wholefood/healthfood shops (try Julian Graves). It may also be available if you have an Asian foodshop in your area.
Local shopping experience (southeast England)
Look here - there are enough for you.