If you live in the US, you could use Privacy for this (privacy.com). Not only do they allow you to create a separate card for each merchant, pause/unpause/close/set spend limits and so on, but their support is so nice that half the time they'll just give you credit instead of making you bother with a proper chargeback. And you can do that over email.
Works even with merchants that don't support PayPal. Everyone supports good old card numbers.
If you contact their support over email they'll enable the option for you to use a card as your funding source. But IIRC you have to connect a bank account first with more than $50 in it and then you can switch to the card.
Works even with merchants that don't support PayPal. Everyone supports good old card numbers.