Hi there, I've got an old Shimano front derailleur that needs replacing on my bike, its only labeling says 'Shimano 105.' The bike has two rings on the front, Shimano 600. It has a mounting piece built onto the frame which I'd like to keep using (pictures below). Can anyone please recommend a replacement, preferably relatively inexpensive, and available to purchase online! Thank you, and if you need any further information please let me know.