How do I get Hazmat Gauntlets?

From this thread, it looks like you'll need an armourer at your base, as that is who will give you the blueprints for them:

Build the specialist terminals at your base, then staff them. One of them is a weapons terminal that needs you to find an armourer. The armourer gives you a mini quest to get the plans for the Haz-Mat gloves.

Over time, the way Hazmat Gauntlets are created has changed.

Currently, you will need to:

• Obtain their blueprint.
  • You can obtain their blueprint via the Exosuit Upgrade Merchant on the Space Anomaly.
• Craft them using 50 chromatic metal and 20 sodium nitrate.