I use this device it would connect to 1/8 male to 1/8 male to this device (1/8 = 3.5m)
Yes this is one of my cars I own, but the FM transmitter is all-in-one it does SD has 1/8 female connection.
This one is neat because it can use any FREQ on the dial from 88 all the way up in the 100 band.
Found my review on this on Amazon it's now $7.95 + free shipping I had paid $19.99 + free shipping a 2 years ago.
Amazon.com and search audiobug, I got one of these when I first got my creative zen mp3 player and it worked extremley well. Only downside is that it takes an odd sized battery (123 I believe) and can get a bit pricey down the road.