OK, I went to Staples, and although it wasn't listed online, I did pick up 3 20" x 30" White Illustration Boards at the store for less than $5 each. Product # 20654 was the correct width to fit the terra clips. They also had 81/2 x 11 Matte White Sticker paper that the tiles and walls printed on just great and then stuck on the board fine. product # 70972 had 30 sheets for less than $14.
I am actually using a drywall knife from Home Depot to cut the board to 3" and 6" sizes.
and I found a pair of Husky Nipper pliers at home depot that cut the 1" wide 3mm indenture for the terra clips to fit into.
Oh, How I would prefer to let Worldworks do the work and just let me purchase the finished product. Alas, but they don't yet have a similarly large selection of terraclip items as they do for terrainlinx.
Unfortunately the nearest Staples to anywhere in Italy appears to be in Germany. Sorry.