I bought a Tune Linientreu so you don't have to. : r/BikeMechanics
Huepar Fine-tuning Bracket Laser Level Adapter, Multifunctional Magnetic Pivoting Base with Adjustable Clip, 360° Adjustable Support with 1/4"-20 Male Threaded, Height Adjustment - PV10+ - - Amazon.com
Fine Tune your rear derailleur with new Linientreu precision laser tool - Bikerumor
Review: Perfectly aligned handlebars with Tune Spurtreu - Bikerumor
An innovative method to tune lasers toward infrared wavelengths
Tune Spurtreu uses a laser to perfectly align your stem | road.cc