Did you know that the syrup called 'Grenadine' available quite readily in good supermarkets/deli's/off licences is concentrated pomegranate juice.
(Sorry if this sounds patronising but I worked as a barman making 'Tequila Sunrises' for ages before I realised what Grenadine, a key ingredient, was!!)
Persian, Middle-Eastern and Indian grocers are likley sources, If you self-squeeze don't bruise the seeds. Bitter.
note : Grenadine WAS traditionally made from pomegranate. Rarely now, at least in the US.