So I watched this youtube video earlier, detailing how to beat the game without collecting orbs:

In the video, he mentions that he found solutions for collecting most of the tougher power cells from speedrunners and that it's not possible to collect the the gnawing lurker power cell in Spider Caves because it lands on an orb.

But there actually is a way to collect that power cell safely, and it's actually pretty simple. When doing an orbless run for fun ~12years ago I discovered that all you need to do is crawl into the power cell. It's been a looooong time but I'm pretty sure that when I collected it I approached the power cell from the direction of the cave entrance. I successfully grabbed it on my first attempt at crawling into it, so I don't know how accurate you need to be (or if you need to be accurate at all).

I don't know if this can actually save you anytime (I remember it always took me a long time to shoot down the gnawing lurkers) but I figured I should tell you guys about it and let you figure out if it's really useful. Maybe it would be faster than backtracking for the power cell in Mountain Pass?