Seiko 0 Shutter to "# 1" lens board

I have a lens in a seiko 0 shutter and a lens board drilled for a number one shutter. I had to have this lens board custom made, and I am trying to not have an other one made. My question is this. Does any one know of a way to make this lens fit on the board I have? Perhaps with a really thin washer? does any one have any Ideas?

Plumbing suppliers have lots of "O" rings, ferrules, adapters, nylon washers etc. in sizes close enough to be worth looking at I would think. In the UK the sizes will be different I expect, but you never know. Cheapest possibility I can think of unless you have a good toolkit.

I've reduced the size of holes in lens boards by cutting a disc from aircraft ply with a hole saw. It's a simple process.
You can make a sample with mat board & hobby knife if you need to visualize it.
The plywood is available from hobby shops and craft stores and should be sealed with polyurethane or varnish.
1)cut the plug from the ply with the hole saw.
2)glue the plug to a piece of ply just slightly smaller than the lens board(inside dimension).
3)cut the shutter mount hole through both the plug and the backer board. The hole used in the plug will line everything up.

This gives you a square board with a raised section that fits the original #0 mounting hole and a #1 diameter filler. The board can then be mounted on the front or back of the lens board with double sided tape, glue or screws.