You don't need to be much of a woodworker to make a good enough lensboard. We aren't talking french polished cuban mahongany here. Well not on my cameras we aren't. If you can't find one then I say give it a try.

Go to the local mega lumber yard with your tape measure in hand. Assuming the measurements in the ad are right then look for a board 4 1/2" wide. Stick to something soft like pine. Only thing to watch for is that it's knot free. Once you find the board ask them to cut it to lenght for you. You'll likly now have enough boards to last two life times. Get a reasonably sharp chisel about the the width of the rabbet and take your time shaving the rabbets. Nice thing about a soft wood is you won't need a super sharp chisel. Every so often stop and see if it fits the camera. Don't rush. Or ask somebody who has a router to make the two rabbets for you. Then all that is left is drilling the hole.

Once you've made your first the second will be childs play. The only thing to watch is you find a thin enough board. A real lumber place will have resaw services for you but the big box hardware stores won't so don't get anything too thick to mount your lens on. Unless you're mounting long barrel lens then you might want a thick board.