You can a six to two adapter plug at most of the home centers. I've got one in my dining room and it's plugged into a Decora receptacle which is the same pin spacing as a GFCI.

I've never seen a 4 plug GFCI. You can however just install a second receptacle (either another GFCI chained of the protected side of the first one). I did that for my wife's vanity (There is actually four in over the countertop and one in the back of the cabinet so she can leave things charging in the drawers.

The problem is when the GFCI trips.

Many of the adapters cover the entire front of the receptacle covering the reset button, and mount using the faceplate screws.

Enlarging the box and adding more receptacles is not usually that hard unless the wall is tiled.

Home center as in Home Depot and Lowes? That's where I have been searching without success.

http://www.amazon.com/Helping-Hands-Grounding-Outlet-Adapter/dp/B000FK9XA8/ref=sr_1_1?ie=UTF8&s=hi&qid=1261517129&sr=8-1

Thought I got it at Home Despot, might have been Walmart.

Replace the breaker with a GFCI breaker, replace the GFCI receptacle with a standard, then use the adapter you have selected.
OR
Enlarge the box and add more receptacles.

Thanks for the link, ronnatalie.