According to some of the other posts here, there could be another way
to get it to work. You can find that other circuit and use a
double-pole GFCI breaker for both of them.

Ha, ha.

That MIGHT work IF:

1) There isn't any "neutral sharing" other places in the house.

2) You have room in the panel

3) The "other circuit" isn't used for guaranteed "high leakage"
appliances.

4) The owner doesn't get upset if two circuits go out from one
essentially harmless groud fault (a neutral to groud fault will also cause a
trip.)

Frankly, the most cost effective approach is to only put GFCI outlets where
that type of protection truly increases safety. That's where folks might
end up touching a HOT wire while another part of the body is grounded. In
older homes, this means kitchens and bathrooms and basements and outdoors.
With plastic plumbing, the kitchens and baths are relatively safe.

--
Mark Lloyd
http://notstupid.laughingsquid.com

"Democracy is two wolves and a lamb voting on what
to have for lunch. Liberty is a well armed lamb
contesting the vote." - Benjamin Franklin