Well, not really an overlay, but an entire HeroQuest board. Here you can download a 200 dpi version of a HeroQuest gameboard with two-space hallways. Just get it printed out in the following dimensions:
86.14 cm by 68.14 cm
and put a self-adhesive transparent foil for protection over it. You get a brilliant gameboard with more action than you can imagine!!
The throne of the Witch-Lord: Especially adapted to meet the requirements of a 3 x 3 board.
