Repair kits can be had at the dealer, not too expensive. Aftermarket,
probably not. Usually what goes bad are the three plastic pins in the
"clutch" assy. I've found  that you can make your own out of plastic
stock or something of similar diameter but I think the price of the
actual repair kit isn't that bad. Good luck.

If the gear is not stripped and the only failure is the
three plastic slugs that go between the inner and outer
portion of the drive gear and, you are unable tofind news
ones, you can use use a high strength epoxy to fill the
area.  Have everything in place and pour very carefully to
just fill the area previously occupied by the slugs.  Make
sure you clean out all the debris from the failed slugs.  I
have one still going repaired this way for over 5 years.

Lugnut

Some of the gears are available off the shelf. Some can be modified to
fit; in my two Grand Marquises, the inner metal gear is different than
the part popularly stocked. I remove it and replace it with the old
inner metal gear from the broken part and this works perfectly.

One I have here is in a bag marked "Platinum Parts", so it's definitely
not a dealer-only part.

On my way in to work today, I stopped at the Ford dealer. The rebuild kit
was in stock.
New worm gear, plastic rollers, steel center gear and backing plate/seal.
$35 US.

I guess this is a common failure item. Usually the parts I want from the
dealer need to be ordered.
Erich