filler tube relocation - wood bed

[69Tom]

So I just purchased a rear gas tank from Classic Industries as it was on sale. It doesn't appear to come with a filler tube, although maybe I'm wrong.

I plan on mounting the filler tube/opening in the bed floor as it's a stepside. Truck is a 70 C10, SWB with a wood floor.

I'd like a fuel cap that is somewhat flush with the wood floor. Anyone have any recommendations on where to get a good one? Pics would be cool if you have any.

I've run a bunch of searches and didn't seem to find what I'm looking for, hence the new post.

Thanks in advance.