Trying to find out whether a particular part is common to other models is often very difficult but I would have thought that there were enough Mareas being dismantled to enable you to find the pump you need.
First thing to do is to get all the part numbers/ref numbers off your old pump so that you can identify whether any pump you are being offered is the same, then get on-line. Apart from eBay here are three links that are worth trying.