Try this one.
http://www.designtech-intl.com/fm.asp
http://shop.ebay.com/items/?_nkw=fm..._trksid=m270.l1313&_odkw=fm+voyager&_osacat=0
I was personally involved in the design of the audio section of the FM Voyager before Directed Electronics purchased it from the company I formerly worked for.
In particular, I designed the bandpass circuitry that normalizes the frequency response. Most FM transmitters have no such circuitry - and so their end frequency response is nothing like a normal radio station. During developement this unit was compared to literally dozens of other transmitters, some costing upwards of 100 dollars. While this unit - like everything on the market - had its share of reductions/limitations in order to meet cost and engineering goals, the final result was a product that sounds better (in my opinion) than virtually anything else on the market - including the transmitters that cost many many times as much.
As a side note: Some FM transmitters are *NOT* FCC legal. The 12 channel version of the FM Voyager is. The result of being FCC legal is that the power output is limited - and that power can result in some (usually minor) static being received depending on the surrounding environment such as other transmitters and receiver design. In addition, you of course have slightly less channels to choose from, although this is not normally a major issue. While technically innaccurate, the basic thought for lack of better explination is that some receivers have such a low sensitivity that a legally operating portable transmitter may not provide a strong enough signal to eliminate static. The downside of not being FCC legal is primarily that the device could transmitt farther than intended - and it could effect other receivers/stations as a result. There is an older 14 channel version of the FM Voyager, but thats all I am going to say about it.
Call me biased, but its the transmitter I use exclusively and I am very happy with it.
DISCLAIMER: I do not, and never have worked for Directed Electronics. The information from this post is based on first hand knowledge acquired during employement at the company that was originally responsible for the dwevelopement of the FM Voyager. Its possible the design has changed and as such it is possible that nothing in this post is meaningful or accurate at this time.
Kieth