Can we backfill customers with a new entitlement for a product they've already purchased?

Hello.

As above really.

We’ve been selling a product for a few months and have 50-60 customers who have bought it. We’ve realised we need a new entitlement for this product, which I've created, and I now need to update everyone who has bought this product to give them this new entitlement.

Is this possible?

Thank you,

George