DIY ignition shielding?

Folks - First time use of a handheld around my Tcraft. Flipped the
prop and turned on the handheld (using an external ant. mounted below
my feet) and the magneto noise became very apparent. My instructor/A&P
immediately advised that I get a shielded harness and plugs, which
would run about $300. Seems to me that a home-brew solution would be
possible.

Is anyone aware of anyone having done this successfully?

There seem to be two issues to be addressed: shielding the plug and
shielding the cable. I think I can do the latter with shielding taken
off a suitable diameter piece of coax. The question then becomes "How
to shield the plugs?"

Any suggestions are appreciated - Mike