Have you contacted an agency or someone like Gott & Wynne. As Morgan specialists they may be able to access policies that have been used for something like this before?
https://www.gottandwynne.co.uk/ Many new cars (Audi, MB) now come with a short term gap insurance to allow you to sort out your own cover so they must exist. Perhaps it might be worth mentioning to Morgan that they would benefit from having this, even as a costed option to enable it?
Short Term Insurance is also an option and offered by companies.
https://www.confused.com/car-insurance/temporary However I don't know if this will be offered to non-UK resident?
In the past I used A-Plan in High Wycombe for specialist car insurance and they had access to many different policies?
https://www.aplan.co.uk/high-wycombe
