What are the differences between the Sonos edition and the non-Sonos edition?

The sonos edition comes with a preamp embedded and the acrylic disc is superior to the metal one that comes with the non-sonos edition.

Since Sonos is merely a reseller, and doesn’t have control over whether Pro-Ject is capable of refilling the stock, you may be better served by asking Pro-Ject directly.

It seems unlikely to me that the manufacturer would make a fundamental change such as including a pre-amp, purely to be sold via a particular retail outlet.  I suspect that this is just a branding exercise and that the same spec is available elsewhere.  I’m not sure of that, but I do think that either way, the manufacturer is likely to be able to tell you more than Sonos about availability and timescales.

It's back in stock :D

Happy days!