Breathable and waterproof are opposites.
If you are not into competitive performance a rain cape will certainly allow ample ventilation and keep you free of rain.

I have and like this: https://cleverhood.com/collections/capes-2
The Urbanaut has arm holes, heavier gauge fabric, and is a touch bigger for a given size than the Rover. It is high quality gear intended for a lifetime of service. If you are super savvy, you can wait for a %-off sale. But, those can be sort of rare. It may be one of those things where it might be better to just bite the bullet and pay full price. A buy once, cry once, sort of thing.