Ariston Eurocombi pump ?

Hi, I am looking for a replacement pump for Eurocombi boiler unsure if a A/23 or an a/27 but enderstand pump is same . Part number is 997515 which is a Wilo pump , but ariston tell me this has been replaced with a 99663 Grundfos which is 3 x the price @ £100. Can anyone confirm this is correct i have seem Wylo pumps (RS50 model) available @ £30 - is this the same part or will it work in the boiler ?