Fumoto oil plug
 

Before I attempt to fabricate one, anyone know if there is a locking mechanism for this valve so that it does not accidently open?

Thanks
Mac

Yes, there is a spring that holds the lever up and keeps it from popping open. To open the valve you have to push down to compress the spring, then slide the lever open.

They are $20, not sure it's worth all the fabricating, and risking something going wrong in such a critical area of the engine, but by all means go for it. You could be a better machinist than fumoto's, who knows . :)