Does anyone know where to get adjustable stock?

[Butters149]

I’ve seen them sold out all over.  I live in California and was wondering if it’s still legal if I Pin it.

[Vertigofirearms]

Your best bet is to order from benelliparts.net when it appears.

There's different ways to make it compliant. The easiest manner is to buy the kit that replaces the button.

[Butters149]

Where can I get that kit?

[Vertigofirearms]

Assuming you are talking about the M4 series, 

https://www.calguns.net/calgunforum/showthread.php?t=1507997

OR

you can order a roll pin and dissemble the stock and drop the pin in.