No, there are lots of alternative USB charging sources, Sonos doesn’t restrict you, other than of course restricting the amount of voltage/amperage, which you can find on the sales pages for these two products. 

MOVE does not support wireless charging. I doubt that you’ll be able to find a generic charging ring.

All Sonos products that accept wireless charging can be charged by a standard Qi charging pad.  There is nothing proprietary about Sonos’s use of Wireless charging protocols, so unsure why you feel the need to make such a statement?

As above have mentioned,  the Move (1 and 2) is not a Wireless charging product but adheres to EU rules on having a USB C charging port that can accept charge from any correctly rated charger, detailed in the product info.  The ring is just a convenient way to charge, the charging Brick on the new Move 2 is also a USB C charger that can be used for other USB C charging needs.