Dommie Timing cover wanted Classified expired

For 1959 Model 99 I need a timing cover, complete and in very good condition.  I am not very knowledgeable on the twins; so advice also needed. The one I have is the early type with a nasty pressure relief valve system. I believe, later on the timing cover was modified with a better system. Am I correct and will the later type fit a 1959 Model 99?

Thanks for the advice

Will pay good price or have some great swaps

George Cohen

geo@norton.uk.com