E&G is good and local.
I picked up the kit of Weather-tite connectors from Summit a while ago. I don't use a whole lot of them, but I periodically restock it.
Besides Parts Express there is Waytek and Delcity. I've also used Wiring Products, which is smaller.
'91 Toyota Pickup
'09 Kawasaki KLR650
'12 Gunnar Rockhound 29
“Anyone who believes in indefinite growth in anything physical, on a physically finite planet, is either mad or an economist.” -- Kenneth E. Boulding