You got a point, so... my bad.
http://www.connect-tech-products.com/index1.php?subtype=3.5mm%20Plugs&id=2
http://www.redco.com/Mini-3-5mm-2-5mm-Connectors/
http://store.haveinc.com/c-785-mini-trs-connectors.aspx
http://www.switchcraft.com/Category.aspx?Parent=987
http://www.markertek.com/Connectors-Adapters/Audio-Connectors/3-5-2-5mm-Mini-Connectors/Connectronics/35-4CON-LP.xhtml
The last one is the smaller one, but you can always contact the first website asking
The viablue t6s small has a relatively low profile
http://www.avoutlet.com/index.php?dispatch=products.view&product_id=1580
And last, you can always use ebay:
http://www.ebay.com/itm/3-5mm-3-Pole-Male-Repair-headphone-Jack-Plug-Metal-Audio-Soldering-Back-cover-/261185689713?pt=LH_DefaultDomain_0&hash=item3ccfe15871
http://www.ebay.com/itm/3-5mm-4-Pole-Male-Repair-headphone-Jack-Plug-Metal-Audio-Soldering-Back-cover-/261185689517?pt=LH_DefaultDomain_0&hash=item3ccfe157ad
http://www.ebay.com/itm/Silver-3-5mm-Male-to-Female-Plug-Earphone-Jack-Audio-Adapter-For-Phone-MP3-/261020950779?pt=US_Audio_Cables_Adapters&hash=item3cc60fa0fb
http://www.ebay.com/itm/New-3-5mm-Male-to-Female-M-F-Plug-Jack-Headphone-Connector-Audio-Extension-Cable-/380589320395?pt=US_USB_Cables_Hubs_Adapters&hash=item589ce428cb
Enjoy your headphones