I looked into the fancy harness things that are available but before getting very far came a little improvisation with what I have on hand.
Lo and behold my first try ain't half bad. I don't know if this is some kind of luggage strap or what, but all I had to do was bend that hook from a bit of sturdy wire (I think it may have been a fly-swatter handle).
Update: This isn't the end-all. Today I'm using a combination of what's shown with the trad neck strap.