There are 2 options available to you.

If you already have an amplifier/receiver for your passive speakers, a Sonos Port can connect to your existing equipment to allow you to stream music.

https://www.sonos.com/en-ca/shop/port

If you only have the passive speakers, a Sonos Amp will allow you to power them.

https://www.sonos.com/en-ca/shop/amp

All speakers require power and audio signal.  A passive speaker get power through the speaker wire along with the audio signal...which all comes from the amp/receiver.   Sonos does sell an amp to power stereo speaker channels, but not sure if that meets what you’re looking for in terms of being ‘wireless’.  They also sell a port, which provides audio to your 3rd party amp/receiver.

Are you wanting some sort of mini amp that can sit next to, or attach, to a passive bookshelf speaker and  essentially act as if it’s a Sonos One or Five?  Sonos doesn’t do anything like that, and I can’t imagine they ever will for a multiple reasons.

However, there have been some DIY types who have taken apart ikea bookshelf speakers, removed the computer/amp part of it, and then connected them to higher quality speakers or subs.  You could improve the quality a bit that way, but the amp and tuning are designed for the ikea equipment, not whatever you’ve cobbled together.

Correct, looking for a tiny amp, that can connect to the conventional passive book speaker.

Sonos doesn’t make anything like that.  I’d be surprised if they ever do.

You can do some interesting things with a Raspberry Pi with a amplifier plugged onto the expansion port. I converted one of my ancient Play 5s into a wireless audio player once Sonos bricked it to qualify me for an upgrade discount.

Sadly Pi are in short supply right now.

Hi @FMT 

Thank you - I've marked this thread as a feature request and it will be seen by the relevant teams for consideration. Keep the ideas coming!