Hey Rod,
...I'd be very surprised if you could find all you need in KW... West Marine is pretty much the only game in town for charts (Los Cubanos has some, but no foreign charts to my knowledge) At the very least, I'd give the WM stores in Marathon and KW a call to see what they have in stock, but I doubt they'll have much of anything outside US waters...
Bluewater in Lauderdale is definitely your best bet... Stopping there is not all that much of a hassle, actually... You can anchor in Lake Sylvia (with your draft, you'll have to give the shoal at the entrance a very wide berth off to the east, really hug the shoreline on the left as you go in), then dinghy across to the canal just south of Lauderdale Marina... either tie up at the public launch ramp on the right as you enter, and hike around to Bluewater, or go all the way to the end of the canal to the Southport Raw Bar and use their dock... They will charge you, but not if you have something to eat there... there may be other options to tie somewhere along the south side of that canal, as well...
Or, you could take a slip at the pretty reasonable Las Olas docks just north of the Las Olas bridge, and catch a bus over to Bluewater...
If you really want to avoid going into Lauderdale, another option could be to rent a car for the day, and just drive down to Bluewater... Doing that would allow you to easily hit other places like Sailorman, and MacDonald's Hardware, as well... From the North Lake Worth anchorage, there's an Enterprise location within walking distance. Or, Old Port Cove Marina is surprisingly affordable for that area, they discount Boat US as well, and Enterprise is very close to their location... OPC is a very nice place, highly recommended if you're up for a marina stay, doing laundry and whatnot...
Good luck, but I really think Bluewater is your only option to be walking into, and back out the door with everything you need...
best regards,
Jon