It's not been covered before but another member has been asking me about that in PMs recently.
It is, unfortunately, not any standard tubing diameter. I reverse engineered the dimensions for it from photos figuring it was probably some rim that I would never find. On my model I ended up turning the part on my lathe and bonding it in place.
What I'm going to do is draw up the part as a 3D printing file which I would recommend printing at Shapeways in their Ultra Detail Plastic. Shouldn't be very expensive. I'll also post dimensions if someone has access to a lathe and wants to turn the part themselves. Going to do the same for the turret base ring that goes on top of the canopy.
It is, unfortunately, not any standard tubing diameter. I reverse engineered the dimensions for it from photos figuring it was probably some rim that I would never find. On my model I ended up turning the part on my lathe and bonding it in place.
What I'm going to do is draw up the part as a 3D printing file which I would recommend printing at Shapeways in their Ultra Detail Plastic. Shouldn't be very expensive. I'll also post dimensions if someone has access to a lathe and wants to turn the part themselves. Going to do the same for the turret base ring that goes on top of the canopy.