"They make GFCI receptacle/switch combos but the local BORG may not
have them. Try an electrical supply house if you can't find one at the
big box"

That doesn't solve the problem. What he has is an outlet that is wired
so that one half of the outlet is wired direct, while the other half is
wired to a switch somewhere else. This is fairly common. The only
solutions are to either put one GFCI in another upstream outlet that
feeds both, put one GFCI upstream in both circuits, or put in a GFCI
breaker. I think the latter is the easiest and best.