Torx wrench

The bolt that secures the door stop bracket to the body of our 987 is loose. I have now tightened it twice, but it re-loosens with use because I can't get it tight enough. My primary issue is that none of my Torx wrenches seem to fit precisely in the bolt head.

I'm looking for some advice about what kind of tool to buy or borrow that best fits the bolt so I can tighten it more securely. I really don't want to round-off the inside of the bolt head with a third attempt...

Door Stop

On my 986, the door latch bolts are triple square (12 point), not Torx (6 point). I believe they are 8mm. ~$5 at most tool stores.