Ok so it's only a rear site and as much searching as I did (quite a bit by the way) I could not find one that I could for certain say would fit the Gladius G17 so pleased to find the sight even if the UK didn't sell them and even though it was about 8 quid! What I was surprised about is the sight was sealed in the usual APS plastic wrapper but on inspection the finish was horrendous. Looked like someone had taken sand paper to the front of the sight and the rear white painted segment designed to glow in the dark was poorly finished. Pleased to have a sight but it is only that.

SecutorGladius Rear Sight