You get this quest from Smiling Ranin and Lorund who are constantly bickering on the docks Meridian Village. They want you to get a Snapmaw Lens and a Longleg Lens, not a huge undertaking. This Errand is best completed by, strangely enough, ignoring it and carrying on playing the game. It’s almost a certainty that you’ll come across the parts you need as you play through. If not, once you have the Shadow Sharpshot Bow, you can use Harvester Arrows to increase your chances of getting the parts you need. When you have them, bring them back to the guys for your reward.