In which case the screw version may fit as well? Here's a parts diagram showing the screw version.(And unshrouded barrel).
Would a 300 unit fit? I don't know the corresponding barrel diameters from memory. There's more likelihood of finding one of those, 150 spares are few and far between.
Here's a link to Garvin's post with a scan of the 150 instruction manual if you haven't seen it, just for interest.