I haven't gotten my 3125 yet, but this audio jack was a big issue with me. The phone is due to arrive tomorrow ($0 from letstalk.com) and I will be ordering the jack soon from:
https://www.mobileplanet.com/p.aspx?i=138247
$16 is a bit much, but hey, it's available. But by the time you add the $8 shipping.... what a racket!
BTW. I loved my MPx200 until it got stolen. I've been without a smartphone ever since. I didn't want to replace it until something decent came along. I think it has...