You'd probably have better luck finding a Bluetooth or old low-power FM broadcast setup and plugging it into the side of the HP1. If you go with Bluetooth, you just need to find a dongle that will connect to the HP1 and broadcast your sound to the Bluetooth speakers.
I bought one of these to broadcast to BLuetooth headphones. It works great. Plug it into your headphone jack hit the sync button and hit the sync on your headphones or bluetooth speakers.