With all of these locations below, you'll notice a buff on the screen stating "Cayde's Stash Nearby"
Found in Firebase Hades. The second entrance found by teleporting from the Sunken Isles.
Found in the Wraith Mines area.
This one is a little tricky to get to. Teleport to Exodus Black, and make a sharp right. Follow the path down the slope and walk past the teleporter. You'll find it in no time.
Way down south past the Jetsam. Stick left and you'll make it.