There is a big long discussion about → Updating Firmware using Oticon EXPRESSlink3. @GeekMan did it. Save your settings first as they will be destroyed. You can then reload your settings later after the firmware update.
I think that EXPRESSlink3 uses the same Mini Din-style cables as a Hi Pro. Though I don’t know that for sure. If it does it would be standard CS44 and not Phonak CS44a with pins 3&4 reversed.
The Hearing Club for Flexstrips $20-a-pair → Programming Adapter choose size 10, 312, 13 or FLEX STRIPS Comes with two adapters. Though, watch out because you may end up ordering programming pills by mistake. The two are side-by-side and are very difficult to distinguish which one you are ordering.
Where to get CS44 cables?? I dunno? All I see on EBay are Phonak CS44a cables. Maybe these are getting hard to find?
Tip: when searching add “hearing” to help find cables for hearing aids.