Galef imported Zabala Hermanos shotguns from Spain, and Antonio Zoli guns from Italy.
The Companion folder is simply listed as a hammerless 12, 16, 20, 28, or .410 gun.
Value for one in brand new condition is only about $125.00.
I suspect the Companion was made by Hermanos, and I have no idea where parts might be found.
Here's some possible sources. In all cases, you'll probably have to actually call them to ask about parts, but don't get your hopes up. Even is they have the stock parts, they'll likely cost you more than the gun is worth:
http://www.e-gunparts.com/
http://www.jackfirstgun.com/
http://www.gun-parts.com/index.html/