Yes, here is a link to a battery door and long gun swith kit:
https://www.opticsplanet.com/streamlight-tlr-battery-door-switch-assembly.html?_iv_additional-features=door-switch-assembly-69130-w-long-gun-remote-switch
Yes. They have a switch that replaces the battery cap, runs along the trigger guard, and has the switch near middle finger on my Glock. Go to their website, select the light, then open the “accessories” menu.
Of course. Paste "Streamlight TLR-1 HL Flashlight Long Gun Kit" in the search box.
My 2 cents... I think Surefire may be the only company who offers what's called a "tail cap" that has a wire attached to a pressure pad that can be adhered to a point on your weapon/s. Is ideal for people with short thumbs/fingers. My preference is the rigid pressure pad that naturally mounts and is conformed to fit the pistol grip of your prefered pistol. Some don't like it because it requires you to be aware of your manual dexterity and sensitivity on the pistol grip to avoid inadvertently turning on the light. I have alot of experience gunfighting in the dark with this type of pressure switch so it's not an issue with me. I'm highly supportive of LEO and Spec Ops folks using this kind of switch as long as they practice with it periodically.