I really love the look of the Brazillian homebrew HQ set The Quest—and I just saw a video that shows how to make the perfect board for it with EVA craft foam! Obviously doesn't have to be nearly as large as he did his, and you might build it on a couple pieces of good sized chipboard. Here's the video:

Bonus, if you use a large enough pack of EVA foam colors, you might not have to work too hard to match the colors of the HQ tiles if you start with something relatively close to the room tile colors, especially for The Quest where the result ought to look a little cartoony.
<InSpectreRetro> All hail Zargon!!! Morcar only has 1BP.