specialty cylinder base wrench needed

On a narrow deck IO360, the top aft nut on the #4 cylinder has interference from the rear of the engine case on a standard cylinder basenut wrench. I got lucky in that a local A&P had a specialty wrench that was offset a little and had a bit of angle in it, and it worked fine. I haven't been able to find one of those for sale from the usual suspects, but I'm betting there's a gray beard or two on the forums here that have seen it and know what I'm talking about.

Where can I get one of those, or do I have to chop/weld and make my own?

I have had the cyl's off twice on my N/D 320 (thought it was the same case). I remember a nut or two having a limited rotating swing clearance, but had no issue using the standard wrench. Unfortunately, I can't remember the details of my approach to the challenge. the nut is a 12 point, so you only need a 30* swing clearance. Some side to side wiggling will help to get the wrench seated while in tight clearance.

Larry