There you go bro!
http://www.ebay.com.au/itm/3-5mm-Impedance-Adapter-20ohm-75ohm-100ohm-175ohm-for-HiFi-Audio-Player-Earphone-/272428465695?var=&hash=item3f6e007e1f
msl3vGtZnwXprEITP58EDow
http://www.ebay.com.au/itm/Short-Universal-3-5mm-Male-to-Female-Stereo-Audio-Extension-Cable-4-Pole-b5-/322062767956?var=&hash=item4afc6fd754
m6mKd2o79BdppBy6dB5yMAg
The phone won't damage your headphones unless you go silly with the volume. Make sure you are down to say 30/75 and go up from there.
You need to connect the headphone, adapter and extension together. Plug the lot into the phone and switch high impedance mode on. Leave the extension plugged into the phone, remove the 100 Ohm adapter and plug the headphone back into the extension. As long as the extension is plugged in, the phone will remain in high impedance mode.