Cheap solution is a bluetooth headset with a smartphone or iPod.
You can also send your radio here
and tell them you want the headphone output installed. Looks like a $105 job, but you can probably kiss your radio warranty goodbye.
2012 FLHTCUI, White Hot Pearl, Master Tuner, DIY gutted headpipe, H-D heated grips, 1" floorboard extenders, VStream, HDPD+, J&M Rokkers (thanks, Falc!)
2004 FLHTCI, Solid Blue - sold
1998 FLHTCI, Laser Red Pearl - traded
1996 FXDL, black/violet teal - traded
1992 XLCH1200, black - sold