Where can I buy a 3.5mm headphone jack?

A Headphone Jack (3.5mm) is a small round connector for accepting the pin-shaped plug from a standard pair of music headphones. While 2.5mm is the standard for phone headsets, the slightly larger 3.5mm size is the standard for music headphones and just about every other type of electronic device other than phones (music players, PCs, etc.). But there are phones using a headphone jack 3.5mm now. So I found this 2.5mm To 3.5mm Stereo Audio Jack Adapter (3 rings) Elago Brand for $1.49. This is 2.5 mm Male to 3.5 mm Female. Use 3.5 mm Headphone on 2.5 mm device with stereo sound but not compatible with BlackBerry.

I also found this Stereo Headphone Adaptor with 3.5mm for Motorola for $2.99. This Stereo Headphone Adaptor with 3.5mm for Motorola is fit for the following Motorola model: E1070, E770v, L2, L6, PEBL U6, RAZR V3, SLVR L7, V360, V3i, http://www.V3x.It allows you to listen to MP3s or FM radio on your Motorola handset with your regular headphones (3.5mm Jack )and Motorola handset connect to computer speaker , HiFi and amplifiers easily.

Here is another Headphone Jack Splitter 3.5mm 1/8" Stereo Mini Plug for $1.96.