I don't think there is any Custom Android firmware available by the third party developer based on ICS. But you can check the software update manually by going to settings > about phone > software update.
If you don't find, find a community of tecno n3 users and all together send an email to tecno support website. I guess, this phone was released in Kenya and Nigeria (mostly Africa). Please go to the nearest support/service centre and ask them about the ICS update. In initial impression, this phone is capable of running ICS 4.0.1 as it has got good speed and RAM as well.