Westie1 is recommending the Magpul MOE I think. It's a quality very inexpensive handguard to swap with the factory Sport II handguard. The Magpul MOE allows you to add the stuff you want to add without buying a quad rail or quad rail sections, that's what the M lok system does. You can buy M lok mounts for both a flashlight and a verticle grip and attach them right to the MOE handguard. Quad rails are out, they are heavier and are very uncomfortable to hold, M lok and Keymod handgaurds are in.

Flashlights are hard to recommend because there are a whole array of them out there and a lot depends on lumens and quality of the light. Find one in your budget and buy it. Streamlights are very popular.

Red dot? Again, what's your budget. Aimpoint or Trijicon are the best IMO but expensive. Primary Arms makes a great budget red dot too so figure out what you want to spend.

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Still carrying my S&W 642