I don't think the current offerings from IthacaGun are marked 'RayBar' if that makes a difference to you.
They simply call the sight a fiber optic now
6/48 Thread Designed for Vent Rib Barrels, for smooth bore grind shank to be flush with I.D. of barrel
ithacagun.com
Up to a couple yrs(?) ago I believe they still offered the orig RayBar.
Maybe they still do and I've just not been able to locate them on their site.
The ones Numrich offers are the non-Raybar marked ones.
You can usually find orig's on Ebay. Lots of people took them off of their guns over the years. Most real Gunsmithing operations usually have a shotgun front site bead 'jar' of take offs on the bench, There's generally a couple RayBars in there. Finding a real gunsmithing shop is the tough part.
The stud on the sight has always been a #6-48 thread on the M37 pump. That's a standard scope mount and sight mount screw size.
The Raybar on the M37 had 2 bands securing the catapillar bead up till about '74 or 75. Then they switched it for some reason to a single band securing the bead.
Probably saved a 1/4 cent per unit in vendor costs in desperate times...