Tow Hook on Cessna 180?

Just purchased a Cessna 180 and hope to use it occasionally for glider
towing. Found an STC for hook installation by Javelin Aircraft which
seems not to be around anymore. Gasser Banner says they don't have one.
Having towed behind a C-180 at Seminole Lake I know it is possible. Tim
Mara says Karl Streideck tows with a C-180. My A&P says if I can give
him some sample 337's it will make things a lot easier. Anybody out
there willing to share a copy of their field approval for a hook
installation on Cessna 180's??

Stuart Grant