"If I'm not mistaken the washer you need is a huge brass friction washer". It's brass for a reason
I happen to have mine spare because I couldn't use it in the brase-on's on the frame I fitted my lever too. Cut a long story short " I botched mine onto the frame ". It works, but to the "purist" it's a naughty fit.
Anyways, if it's the brass washer you're after "You can have mine"
I won't be taking the levers off anytime soon now that they work. Be warned "setting the indexing to the setup you describe can be very very testing". Setting mine drove me nuts (can't rememebr why though
it just did). Your call buddy, "fit the indexed 1 you have OR buy another but friction. It might save you a lot of headaches". It is the latter route I will take 1 day (when I acquire original frictions back).
Later, yours Laz.
PS: The hassles where something to do with the brase-on being a tadge too short, then when fitted, the large barrel didn't like the block and wouldn't jump clean from 1 gear to the next. Each click of the index was either too short OR too long, and after 3 changes it was almost mid block. Something like that.