Rain protection when cycling?

My 2e hasn’t arrived yet, but I’m excited for it. I will be using a quad lock universal adaptor to mount it to my bicycle for navigation. Only concern is I live in the UK where it is very wet. Quad lock sell a ‘poncho’ which goes over the screen to stop it getting wet, but it is device-specific. Obviously there isn’t one for teracube (yet!), however I was wondering if another phone’s dimensions might be similar enough for it to fit? For example glass screen protectors for the Huwaei Y6 fit the 2e.

Any ideas? There are of course other mounting systems that provide rain protection, but I’m really interested in quad lock.

Huawei Y6/Y6s and Honor 8A have the same screen size. There might be more phones with same/similar screen and hence similar dimensions. However we wouldn’t suggest having the phone without the case.

Other idea could be a ziploc or similar bag that can be sealed.