My mistake, on two counts. First I forgot they changed their website a while ago. You need to click on the Digital Lounge tab once you log into your account on www.sprint.com .
Second, is that you are correct they only offer software for the Mogul. When you click on Ringtones in the Digital Lounge it only offers software to manage your ringtones on your phone.
There are LOADS of websites that offer free ringtones. Do a Google and you should have more choices than you could choose from. Then simply copy them into your Windows/Rings folder on your phone and then assign it as a ringtone.