Replying to my own 10 year old thread with what I think is a pretty good solution. 8AN 6061 aluminum pipe plugs and matching nuts:
https://www.amazon.com/gp/product/B0989Z329Z
I've gone 10 years with just a PVC pipe plug and PVC nut. No leaks, but there's no UV protection in the PVC and it's got to be aging some. I feel better with solid aluminum!
