These are some "low-noise" FET input OpAmps which are all still alive:
not exact substitutes for AD743 but lower noise of all alternatives that I've come across so far.
AD743 is discontinued. We have a few in stock, and there are still a few SOIC-16 version that you can buy.
But better to design with a op amp that is replaceable into the future.
I checked with some replacements of opamp at stage 1 to reduce the noise due to current noise. It seems AD743 is the best balanced opamp for this location. Attached is the circuit schematic of this final version v3.2 , with LISO analysis and also the analysis done to reach to this opamp.