17" Tyre sizes, when stock isn't an option.

[Newsguy]

Thanks Starter!

There is a reason Porsche engineers sized it that way. You probably won't like the handling with narrower rears. I don't blame you for getting off run-flats. They are terrible.
Are you unable to buy online? I would look for Contiis or their cheaper version, General GMax, but those Yokohamas would probably be great as well.
Quick search showed these: https://www.amazon.com/225-45R17-CONTI-EXTREMECONTACT-SPORT/dp/B0BFKYP9KL/ref=sr_1_5?crid=1SIAQU7TO0NPN&dib=eyJ2IjoiMSJ9.d0ug08P5cjXt-P1AvF9wKA-YdR2Glo-FaIQMQbW9mI9YOIDawDqo123UOuSs27sykW92qrnZOSYeaAqvf d4p0xGVksDHirUZgcvUx7-T0SNDWtPshtSVYcdR666YPMna8WYf-jtR2KYdW9d4wGsn1x5Ymnn5rzCUBP1CAl9nCiLlS9rVlMlqH9S lAHTpuB1U0a0prx80WaswTdgL_ADt7GMrzl012THUjMjF-5jKOYkUN955McaVFSZ6CrF6aoFt-8cxuTo3nhvONkNBRD0NsKiqRwbypanSpkUmaFw9z30.DvoXzsu 9pPHFrbOSOaBxK_ooNt-Q0XDhGIM-LdNpwK8&dib_tag=se&keywords=continental+sport+contact&qid=1743599743&sprefix=continental+sport+contact%2Caps%2C114&sr=8-5

I'm sure the rears are available there as well.
Lastly, I don't know anyone using Goodyears on a Boxster (though obviously someone is somewhere.)
Good luck!