Does anyone know where I can get a breech plug wrench for my TC Hawken?

You do not remove the breech plug on your Hawkins. Leave it alone. Granted many years ago, (about 30) the breech plugs were able to be removed, but only for emergencies. The newer rifles do not have a removeable breech plug. The only thing you need to take out of the rifle is the nipple. Even the bolster clean out screw is being removed from many of the rifles and in some rifles, they seem to weld themselves in place anyway.

So just get a nipple wrench/wedge puller/hammer combination tool and you should be all set.

Why do you want to remove it?

I have had it since 1983'-84' and want to see if there is any rust. But Mostly I want to see what is in there. Curiosity I guess, I have stripped down to pieces almost all of my shotguns rifles and pistols and I want to know what is going on in there.

Plus it is another tool for the bench.

I would think a bore scope would be much better for the thing you want to discover. I am not sure if there is any weld on the breech plug you have, but trying to remove it could damage it and effect the accuracy of the rifle, not to mention the possible integrity of the rifle for safety. I'd contact Thompson Center by phone and ask their opinion.