First, I'm in the US. I have 7 Soundbridges: 5 here in the Phoenix area (3 in service, 2 spares), and 2 at our "heat getaway" in Oregon. Second, I have some electronic experience, so what I mention here is for those with similar backgrounds.
I blush to say that, when needed, I buy my Soundbridge (SB) power supplies at thrift stores, such as Goodwill, Savers, etc. Recently the bedroom SB began making a sputtering noise not related to the powered speakers serving it. I checked and found that the SB's power supply appeared to be an original, rated at 1.5A. I had a 5V/2.6A "Goodwill" unit but it had the wrong 5V plug for the SB, so that had to be swapped out, being careful to observe center=positive when doing so. The SB's running again, no more sputtering noise, and I anticipate a good life for it.
Regarding buying power supplies at thrift stores: Most units found there were associated with, but are now separated from, other stuff donated there. Their price is usually $1.00 - $1.99. You find them hanging by the dozens on hooks. I buy only "switching" types, NEVER the heavy transformer units, and only 5V DC Out units with output current rating of 2.0A or more. The unit ratings are usually printed on the outside of the unit somewhere. The correct SB plug, if you don't have one around, can be found at a Radio Shack or similar store. Some soldering skill is required; if you don't have it, there's usually a neighbor around who has. Most importantly, before plugging into the SB, be absolutely sure that the center terminal is +, and that the open circuit output voltage is 5.0 - 5.3 V.
3 SoundBridges, 1 SoundBridge Radio - Phoenix, AZ
3 SoundBridges - Netarts, OR