I ended up making my own additional tiles for use with the fan-made options available. However, the same technique would work equally well with the dev kit tiles. I simply printed the custom tiles on full sheet labels. I bought them from Amazon. It's basically an 8.5 x 11 sheet of sticker paper, but not glossy. Most of the custom tiles are already to scale, so print them directly onto the label sheet at "actual size", cut them out, and stick them on. In my case, I used matboard bought from a craft store (like what you'd use to create a fancy border for a framed picture). It's cheap and happens to be just the right thickness to match the tiles from the game. I put those printed stickers right on there, then I color the edges black (personal preference) with a sharpie. They shuffle just fine with the base game tiles and you can't really tell them apart other than the gloss vs matte of the printed ones. Still, we've had great success with that technique so far.
print the sectors onto sticky labels (you can get full page labels) and stick them straight onto the dev tiles.