MG Car Repair: installation of thermostatic switch in radiator, pep boys, retaining clip

Question
I just installed a new radiator in a 1980 MGB . The thermostatic switch bulb was simply pushed into the grommet on the old radiator with no retaining clip.  I ordered a new grommet and retaining clip.  The grommet is not thick enough to lock itself in place securely with or without the retaining clip.  When the switch bulb is pushed in the grommet this tightens it some but not enough for me to think that it will stay in.  Do I need to super glu it.  I tried the grommet from the old radiator with not much better results.  I have a 1977 MGB and the hole looks to have been welded up.

Answer
Clifton:

It's hard to say if the hole has been worked on.  You could try a larger generic grommet - try a local auto store like Pep Boys, Advance, etc. Failing that, you could install with some permatex non-hardening gasket sealant (#2 I believe).  Good luck with your efforts but sorry that is all of can think of right now.

Brian