It seems you have a Tiagra 9-speed triple front derailleur with a 31.8 mm (1-1/4") diameter clamp. They aren't that expensive if you find a direct replacement but a 1-1/4" clamp isn't all that common. You may do better to find a 1-1/4" diameter accessory clamp and use a "braze-on" front derailleur. You could use a 9-speed triple front derailleur from the 105 group too and it would be a FD-5503.