An update if anyone is following this.
I have chosen violence, also known as trigonometry. I’ve decided to use the player’s camera position and the position of the sun to try to fake the godrays, as everything I have found so far is way too expensive/useless for the quest. I am not sure if I can share my math with everyone, but if you think about it you can probably figure out what I did. I will share how it turns out if I can get it all working!
Let me know if anyone else is interested, or has some coding Post Process Materials in UE4 in VR advice. Thank you!