Here's what I worked out after finding my starter button turned to dust...especially since I found it NLA from Honda and $125+ from pirates. I found a suitable switch at Ace Hardware ($7.00) you have to dremel out the housing a bit at a time until it fits snug in the housing and drill out the hole slightly to where the threaded part fits thru...I was left with an extra wire which I just taped over. It's been working fine for about a month now. I was afraid the leads might melt, but it seems they are up to the task so far.
CB400F Starter Button