My neighbor had one installed in his golf cart at Best Buy. You can pick up this one for $38 at BB. The biggest expense will be the installation, probably $150 to $200 at BB. Their website said the Lady Lake store has 3 in stock.
SiriusXM Stratus 7 Satellite Radio with PowerConnect Vehicle Kit Black SSV7V1 - Best Buy
This one is on sale at BB for $30, they can get it in 3 days.
XM Onyx EZ Satellite Radio Receiver with PowerConnect Vehicle Kit Black XEZ1V1 - Best Buy