Mounts for a 1/4" shotgun vent rib

[TURKEYWHACKER]

I have been having a difficult time finding a base that mounts by clamping to the 1/4" ventilated rib on a youth 20ga I'm trying to set up for my granddaughter. I have a reflex sight I want to mount, but all the bases I have found are out of stock or 3 to 4 weeks until available. Anyone know where I can find a mount? Thanks in advance for any help.

[stinkpickle]

B Square universal will work on anything up to 3/8".  There are adjustment screws on the side for narrower ribs.  I just installed one on an 1100.

https://www.cdnnsports.com/universal-shotgun-cantilever-rib-mount.html#.XGrdx6BryUn

[stinkpickle]

BTW, I cut off the cantilever end.