Paula, here is the page from the Canadian Coast Catalogue . Use the "Previous Page" "Next Page" arrows at the top to see more similar items.
If your pump is the chrome one in the middle, they list a repair kit for it for about $12 CAD. The complete pump is $45. You can order directly from this site or you can go to your local RV dealer with the part # and they can get it in for you. This particular order page is linked to Apache Camping Centre in Thornhill.
If your pump doesn't match any of these, then just pick one out that will cover the old hole. Our older Trillium had the 20345 for use with the freshwater storage tank and it had the 24922 pump on the next page hooked up to the city water supply side.
Thanks, Charlie ! That's the one
I'm going to buy a repair kit and have a go. If that fails, we'll buy a replacement.
Thanks to all who replied. I really have learned a lot.
(I think these little pumps are NEAT !)
best wishes, Paula