I like Jerry's plastic/leather suggestion.
I would use those with
with these anti-corrosion impregnated felt "washers". These seem expensive, but the photo shows rings with a "cut-out" to allow them to be used with different diameter terminal posts. Some sets do not have that feature.
I now use the felt washers (alone) with a 6-volt Optima battery in my 1954 trucks. The rings isolate/insulate the cable ends from the VERY CLOSE battery cover/retainer. No corrosion or shorts in over 10 years.
