The PI Pro Barrier jacket in hiviz yellow is semi-transparent. They have a "clear" version too, but I haven't seen one.

It's an extremely thin, tightly woven fabric that rolls up to a fist sized bundle (or a cylinder about 1.5 inches x 8 inches), so it's easy to carry in a jersey pocket. I found it to be somewhat less breathable than I expected, and it can be noisy in the wind if it doesn't fit tightly. But I really like it's small packed size, and it handles light rain well.

I often unzip it partway to get some air circulation inside. But then it would be inflated, and not very transparent.

It's actually quite transparent unless there's an air gap between the jersey and the jacket:


Rolled up: