Most typical hubmotors use UVW hall sensor position sensing, and most of them use bipolar latching open-collector sensors.
If the A20L is that type, then you can use the SS41 or SS411 variants, which ever one is suitable for the votlage and temperature range of your system. (the different letters are usually for different ranges of those).
If it's not the same in the important particulars as the 41xx types, you'd have to see which one has the same particulars and use those.
Latching or not is important, as the controller being used will have to know if it's seeing the passage of one magnet or two.
Same for unipolar vs bipolar.
output signal type, usually open collector, is important, because if the controller is like all the ones I've seen it has pullups on all the hall signal lines to provide the actual output voltage, and the hall just grounds that to turn the signal on. If your controller does not have pullups, then you have to use a sensor that actually outputs the correct signal type/range the controller expects (0-5v, 0-3.3v, 0-12v, etc), or you have to install pullups (at the controller end, preferably) from the 5v (or whatever the controller expects) to the signal lines.
Supply voltage range for the sensor is important, because many controllers have a diode in series with the 5v supply for the halls, so it is really only 4.3v or less (sometimes as low as <4v). Some (very few) controllers use 12v supply for the halls, some (very few) use 5v supply but 12v pullups, etc. If the supply is very close to the lower limit for the sensor, you may have unreliable sensing when you get noise on the supply or ground lines to the sensors (in the noisy motor cabling environment, that's very common).
Temperature range is important, because these are inside the motor, and while yours aren't in the stator where it can get really hot really fast, it can still get pretty hot in there overall after it's been running a while.
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