Holger,
If your customer would consider INA500A with max offset of 3.5mV, min CMRR of 62dB and max GE of 0.05%, then they are not concern with obtaining high precision. Thus, in this case they may simply use any low cost op amp and add four resistors (with 5:1 ratio) to create their own difference amplifier with a gain of 5 - see below. One may get low cost 0.1% matching resistors that would assure min CMRR of 54dB and max gain error of 0.2% while offset may be calibrated out.
It would be useful to specify IQ, GBW, Vcm and Vout ranges, and express drift in [uV/C]. In the absence of such info, there are many op amps that would meet above requirements - please click on the link to see the list:
As far as resistor matching goes, if the customer absolutely requires better than 0.1% resistor matching, they may use our recently introduced RES11A, Thin-Film Resistor Dividers with various ratios that are matched to better than 0.05% - see below.
