Haven't seen a lot of examples of boards that implement the GA-FC, so here's the one I just put together! (Also posted in r/guitarpedals) : r/BossKatana
NEW BOSS GA-FC Foot Controller for Katana Amplifiers - Eclectic Sounds
Boss GA-FC – Thomann United States
The GA-FC: Unlocking Performance Potential with Your Amp
Amazon.com: Roland GA-FC Foot Controller for GA-112 and GA-212 : Musical Instruments
Boss Katana-100 MkII 100W 1×12 Combo Amplifier, Boss GA-FC GA Foot, 1/4 Cable Bundle | ProSoundGear
Boss GA-FC GA Foot Controller | Reverb Australia
Boss GA-FC – Thomann United States
Katana - Using the Roland GA-FC Controller
Boss GAFC EX Foot Controller | American Musical Supply
Boss GA-FC footswitch - Five Star Guitars
Boss GA-FC Foot Controller | zZounds
Guitar Pedal X - GPX Blog - Boss's new GA-FC-EX Foot Controller Massively Expands on the Control Capabilities for Katana Amps
Footswitch Boss GA-FC
Boss/Roland GA-FC Foot Controller for Boss and Roland Combo Ampilfiers | Reverb