It’s probably best to keep your eye on sites like eBay, pre-loved, facebook marketplace etc. and look for any such devices that are being sold for spares/repair. If the speaker perhaps still sounds fine, you could maybe consider covering it - see this link: https://soundskins.com

Many thanks Ken.

Has anyone else had issues with them slowly vibrating and falling off the table or furniture etc ? 

Not that I’ve seen reported here in the community - I have 4 x Sonos Fives. Two are on small tables in our Dining Room and they’ve not ever ‘noticeably’ moved. The speakers have probably been in situ for 18 months/2 years, or thereabouts. They only get moved when dusting/polishing the tables and dusting off the speakers. Did you not notice it moving when cleaning/dusting?

If that’s what happened in your case, then perhaps see if your Home Insurance might cover its replacement - it’s why we have these type of insurance policies, that’s if you do perhaps have accidental cover for Home contents, albeit with some policy voluntary/compulsory excesses these days - it might be much easier to perhaps purchase a refurbished product and sell yours on for spares/repair.

Put some non-slip material under them.

Gorilla Grip Drawer Shelf and Cabinet Liner

https://www.amazon.com/Gorilla-Grip-Original-Adhesive-Cabinets/dp/B07W6K32W1/ref=sr_1_16

Many thanks to all.