Thanks everyone for your replies, it's eye opening. I wish I had known about the situation of the N-Connector before I opened the front panel.
I was able to press the SMA connector back on and re-solder it by adding some flux and it seemed to take solder well, but I can't say the integrity of this cable is very good now.
I did find one on E*BAY, but they want $50 for it including $10 shipping which seems a lot for this tiny bit:
https://www.ebay.com/itm/351215935948?hash=item51c619e1cc:g:50sAAOSwGWNUWSvZThe original problem I had is the last digit of the display for the frequency was acting up. Dots would randomly disappear or go completely out on that digit. I was able to find another A1A1 display board for $18 on E*BAY.
Just swapping the single digit didn't work, but problem persisted, so there is something wrong with this board, either with bad solder joints or a crack in the board itself. Neither of which I could see from inspection.
I fitted the E*BAY A1A1 board and now the digit seems to be OK, although it doesn't display a 0 only 1-9 which must be by design (milihertz). It does display 0 if I press status button as expected.
These single dot-matrix digits themselves are rare and expensive. I saw some on E*BAY for at least $20. Broadcom makes a modern replica of them, but they're over $50 each on digikey. Really crazy.
If I had purchased one of these digits, the problem wouldn't have been solved.