LM,
You can do a search on EBay for 3.5mm hub and multi point Bluetooth transmitter. The mp transmitter will pair with two devices, but with a 3.5 mm hub you could hook up more than one transmitter. The transmitter uses Bluetooth Version 4.0 so the range is somewhat limited. In my place, going between rooms, the range is about 30 to 40 feet. In a different location the range might be a little less or more depending upon the type and number of walls having to go around and through. The transmitter cost $13 including shipping. The transmitter did not come with a power supply, but just about any micro USB power supply or outlet will work as the current requirement is low. I am currently using a mp transmitter with an Echo Dot to connect to a home theater system in my bedroom, and a Bluetooth speaker in the adjacent vanity area. The speaker is moved into the bathroom when taking a shower. The sound quality is good, and there has not been any problems with keeping a continuous steady connection. However this might not work well while using a microwave near either the receiver or transmitter. This has been a problem for me while using a Kindle Fire in my kitchen to connect by Bluetooth to my living room sound system.