A simple software solution exists if your phone is rooted.
This solution for smartphones without notification LED was released some time ago on forum.xda-developers.com and consist in a small app that hacks either the power LED or the back-light of the soft buttons to give a visual indication of missed calls.
It works perfectly on the THL W100.
After the installation of the noLED.apk app, the setup will try to locate the files to tweak.
Off the 3 locations detected, two are actually usable:
The first one, will hack the power LED for notifications...
... and the third option will use the back-light of the soft buttons.
Once tested from the app, the ButtonLED feature can be enabled from the Accessibility section of the system menu.