There may be a way round it IF you have a cassette player? It's a bit convoluted though.

Sony (And others I think) do a cassette adapter you pop in your car radio that has a 3.5mm audio jack attached. I use this to connect my phone to my car stereo which works great for both music and sat nav. There is also available on Amazon, among others, a 3.5mm female to USB adapter. I think the USB is male though, so you'd need a gender bender too (USB male to female adapter). I'm not a technical person, so can't guarantee that would work, as USB is essentially a digital connection whilst the 3.5 jack is analogue audio, but the fact that there is a USB to 3.5 female available would imply that it may work.

A bit messy maybe, but none of those items should be very expensive to try. I paid about £9 for my cassette adapter and the other bits shouldn't be more than £2-3 each.

Could be worth a dabble??

I recently bought a similar item from amazon for just under £5. The one I bought can play from a memory stick, an SD card and uses a cable to connect to the headphone output from an mp3 player etc. It transmits on FM and has lots of different channels it broadcasts on. It also came with a remote but the only downside is whenever it is switched off it doesn't remember the channel it was broadcasting on or the track it was playing but for a fiver what do you expect. The sound quality is not too bad either, it's better than the older fm transmitter it replaced. hope this helps.