Thread chaser for oil screen housing?

Looks like my threads are hosed up where the oil screen screws in on the
back case of my (Continental) A-65. Heard it mentioned on a Swift
bulletin board that there is such a thing as a thread chaser to (I
assume) re-work the threads a bit and/or to clean them out to prevent
damage to the brass threads on the screen. Where would a guy find one
of these beasties? It's pretty big, ya know...something like an inch
and a half or maybe even bigger...

I grounded until I can get that fixed!! I don't relish the thought of
removing the engine and then taking off the back case for re-work or
replacement (they are probably scarce as hen's teeth)...

Scott
Corben Junior Ace