US Company Selling at a Popup in the UK. POS solution?

Does anyone have experience with selling products overseas, in-person? We are a US-based publication with a US store (and US bank account) trying to sell our products at a book fair in the UK. So far, it looks like in order to sell our products in the UK using Point of sale (card reader/POS) we would need to set up a new shopify store and have it linked to a UK bank account. We don’t have a UK bank account or UK VAT number. One idea we had, was to use a QR code and point customers to our current US store using “pick up in person” instead of shipping as the option. However, the customer would still need to enter all of their information, so I’m not sure if this would be the best option.

Has anyone else run into this problem? Is there a third party app out there that deals specifically with this?

Thank you for any help or advice that anyone has.