[LoganDark]

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.

[astura]

Can only load privacy.com with a bank account last I checked, I prefer to use a credit card.

[LoganDark]

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.

Source: I use a card as my funding source.