Take a look at the link below:
https://www.mouser.com/Optoelectron...e/_/N-b1bc8?P=1yzxr50&Keyword=red+led&FS=True
I don't have exact specs on original LEDs used, but one from that selection is probably as close as can be found in current production. A precise measurement would need to be taken on one the existing part to make sure the outside diameter of the new one can be properly matched to the existing holes machined in the panel.
Once that is determined, it would probably be best to replace them all to be certain the brightness and color is uniform. Most red LEDS that aren't high-brightness types (and these aren't) operate in a fairly standard range of voltage and current, so that's not likely to be a big consideration when choosing the replacememt part.
I suppose you could try to find one from a parts donor unit, the same LEDs were used on the AU-317, 417, 517, 717, 719, 819 and 919 at least.