Old CHT probe replacement

After watching our left engine CHT indicator bounce around the other day, I
decided to pull the CHT probe to look it over. It's ancient, and partially
melted/corroded. So I want to replace it. Here's the problem...

It's not a new style bayonet type two wire probe. It's an old AC (as in AC
Delco) single wire screw in RTD (resistance type device). It looks like a
little spark plug on the connector end and a short thermocouple on the
cylinder end.

It looks similar to the Cessna type probe listed in Aircraft Spruce, but
that sucker is $140 and I don't even know if it would work with our gauge.
(original 1966 Piper single indicator)

Does anybody in the group have a Lycoming IO-540 parts manual handy? I need
to find the current day replacement part number and manufacturer for this
little gem so I can hunt one down.

Thanks in advance!!!

Jim Burns