The flag of Northern Ireland is...complicated. It's what you would call a Geo-political landmine. Any option that QRZ could put in, would upset someone.
Hi there, Northern Ireland is a region of the 'United Kingdom of Great Britain, and Northern Ireland'. Therefore, the British (Union flag) is appropriate to represent Northern Ireland, as this one flag incorporates the St Patrick's cross flag, which represents Northern Ireland, along with Scotland (St Andrew's Cross), and England (St George's Cross) flags.