I believe the Centurions have a plastic bracket stuck to the helmet with a sticky pad, they are a good helmet.
JSP also manufacture a helmet with a pre-fitted lamp clip.
I sell a range of German manufactured helmets made by a company called Voshelme, these also have pre-fitted lamp clips with the clip being a metal bracket drilled and riveted to the helmet. I picked the Voshelme because I thought it was a better helmet at the price, and I like the lumi version ;)
Roy however is spot on, buy a helmet and drill it and you invalidate the approvals (typically EN 397). So all the helmets sold pre-fitted with clips have been certified with that clip fitted. Losing the certification is not an issue to us, but in industry or commercial recreational use it isn't an option.
All that said, whilst the blade mount is still the standard mount for mining lamps worldwide I think most high end caving lamps have moved away from it? Scurions and Rude Noras etc are usually permanently attached I think with the blade mount an option. And the Phaeton used a GoPro mount if I recall? Petal have various options for mounting a range of their lamps to a number of their helmets without drilling.
Blade mount is the best option for a work lamp still. You can also buy a decent elasticated headstrap that takes a blade mount lamp for not much, and KSE make a version called a helmet spider that has clips to stop the strap pinging off a regular hard hat.
my orders are to sit here and watch the world go by