Windfire Wf-501B Torch with Picatinny offset rail mount and pressure switch.
Just a pretty cheap torch, no zoom, no intensity settings, just on/off, but bright and effective. Not owning my own RIF yet this made life so much better at the weekend. I just taped the pressure switch to the loan gun with self adhesive camo tape. Made sneaking around in the dark so much easier than a hand held click on/off torch.
https://www.amazon.co.uk/gp/product/B01MXYEIL6/ref=oh_aui_detailpage_o05_s00?ie=UTF8&psc=1
I even tore it down, reviewed it and added pics.