So you need a ignition with fixed timing, Sad to say right now might be hard to get a new one.
I could kick myself! I saw a brand new in package CH Ignition with Bosch cap advertised as 'the one for Brison singles with mechanical advance" on Ebay 2 weeks ago and watched it go to the highest bidder for $10.00! Always nice to have a spare, especially at that price.
