That adapter in post #4 looks too short to me. Using the one in #2 would be crazy, and I have one for my CCM now. Shims inside are just plain dangerous IMO.

I think changing the stem is the wrong solution anyway.
Just get a monkey bar and lower the stem back down. Far easier to find cruiser bars.

My custom bike has a more common 1" insert, but still I found nothing anywhere close to what I wanted.
So I got pipes at metal mart and hacked them myself. Then took it to my friendly Midas muffler buddy for welding. LOL