So, it appears this is a common problem, and one without a good
solution. Since the compass is useless to me as is, I plan to attempt
a repair before throwing in the towel and getting a new one....

Plan is to drain it and keep it in a "warm" place such as the dash of
my car for a few days to let all the oil evaporate. Then I'll take a
moto-tool and clean up an area around the circumferance of the leak to
accept an epoxy fillet. Before applying the epoxy, I'll put some thin
super glue in the crack to seal any small cracks (and ensure it can
never be disassembeld .

Will report the results in a few weeks.