A Pair of Quality Noise Canceling Headphones (Sony WH-1000XM5)

Specifically any pair of good quality noise canceling headphones, NOT earbuds. The closed back nature of headphones offers much better sound isolation, especially in noisy environments. A good pair will have an audio passthrough setting so if you do need to hear your surroundings you can quickly do so without taking them on and off. My choice are the Sony XM's because you can cup the side and with your hand and it will automatically passthrough audio.

The two most recommended models are the Bose QC and the Sony XM-series. Older versions can be had at a heavily discounted price.