You can start this quest by talking to any of the two partner merchants in Meridian Village named Lorund and Smiling Ranin. They’ll bicker about the machine part that’s fetching a high price in the market. Lorund will stick with Snapmaw Lens while Smiling Ranin wants Longleg Lens. While you’re not required to get both parts, I suggest getting both to maximize the rewards.
If you already have those two parts in your possession, simply talk to them again to complete the errand. Otherwise, keep hunting down the specified machines from their sites/grounds until you get one of each of the parts needed by the traders. Surrender them to the merchants to get the payment for both.
Video Walkthrough