They still make them. They're about $40.I don't know if it was Sirius or XM but they used to make standalone satellite radio tuners which you could plug into an amp and speakers. The other option is simply to open all for window and the hatch and crank it up.
Does each radio require its own subscription or can one subscription be used across all your devices? 9not that I car, I'll never pay for A Sirius, cable, or satellite broadcast subscription.They still make them. They're about $40.