Well I ended up buying the whole flex assembly kit while Mossberg was repairing the original. And the part came back - looks replaced not repaired. Definitely a tiny pin in the button I didn't see before. Anyway, now I have a backup. :p
Here's another question: the Flex version of the 500 has a...
Same thing just happened to my 500 Flex tactical. I cannot find a replacement flex slide tube assembly anywhere. The standard one, sure, but not the flex version with the button.
They want me to send it in for repair, and I'd prefer to replace the part now so the shotgun is still functional...