Coming up: You can now chat directly from the Shopstr offer. The seller can then generate an invoice right on chat for you to pay.
Or if they use Shopstr's checkout, you will see a DM with a Cashu token to be redeemed as payment.
Just keep in mind that many ln wallets do not allow you to generate invoices with large amounts via API. Alby, for instance, caps at 500K sats.