Where do I get the Excellent Upgrade Bench

[Bogan]

Cause I can't see it from any of the traders. Do you unlock it or what?

[Soulphia]

Make sure to check both basics & repairs and refinement sections in the shop, you can also look up every trader in the game, via the traders section of your guidebook

[Aestrea]

Check the watch traders, only one of them sell it and if you were looking at the list of ascended, none of them have it either.