Really? Ive never seen that. Not saying your wrong. Infact, I want you to be right. Show me where I can get that because I want one! lol. But I dont think anybody commercially produces that. It would be custom. and a strange custom at that. Generally speaking, from what ive seen, tapped forward closures are plugged. Ive never seen a forward closure that you can screw an eyebolt into that you can also fill with black powder and do motor eject with.
Also dont see any on the web.
I presume youre confusing this with Giant Leap Rocketry's hard point anchor system. This allows for SHOCK CORD ATTACHMENT with an eyebolt and it has holes for ejection charge gasses to pass through. Though this has nothing to do with motor retention.
Although, now youve got me thinking! Just use a metal hose clamp to attach the shock cord to the forward closure itself, around the neck, below the "bowl" if you will. That way, even if it does blow out of the back, it will all still be leashed together by that cord.
OR... you could use the superglue method to create the friction inside the motor mount tube.