Could you double check the model number please. There is no APL1690, there is however an APL1890 6 burner hob, but I’d rather be sure than give you incorrect information.
model is a Hygena APL 1890 series 90, 6 burner gas hob.
the ignition switch button is on the rhs front of the hob directly below the in line 6 appliance burner control knobs. this is the part i cannot trace.
Ignition button £4.41
Ignition switch – no part number although it is shown on the diagram, if this part is actually required I can ask MFI for you, although they rarely fail.