the exact replacement is part number 21499a as you have discovered correctly.

There is a worthwhile upgrade that many Webasto owners choose however that can often lessen the sound of the pump 'tick' passing through the metalwork - see below link. It's an Eberspacher part number but in this case both manufacturers have the same diameter fuel pump.

https://www.butlertechnik.com/item/Eberspacher/Heater-Fuel-Pump-Holder-221000500300/6TB