Just get a portable unit (XM/Sirius have merged). I have had an older pioneer model and the FM transmitter worked very well. I also have a newer (not to be read latest and greatest) pioneer inno that I picked up as a refurb model for about 70 dollars. I use the portable in my truck, and when I am cutting grass on the tractor I pull it out of the truck and take it with me. Battery is not the greatest. The reception is kinda dicey with the radio only antenna, however, they do make headphones with built in antennnas that people told me work well. I use an antenna off my old unit on my rops if I need great reception.
Don't know if this helps.
This will help - never pay full price for xm/sirius. They are always running a deal, do a search for coupon codes for xm/sirius. Last time I got a year script for about 77 dollars.
Good luck.