1" compatible compression plugs are available but I agree - they are most likely scarce. I seem to recall that I bought one from ti cycles ebay store for like $12. I'm going to check and see if they still have them.

Update: I just went to the ticycles.com website and found the 1" plug "headset compression plug". It comes with a top cap that says Portland Titanium and it sells for $18. The only down side is that it is not very long so it may not give full support for the stem.