Wickes sell Marshal's kerbstones which is very similar, unfortunately they use a generic picture for all of Marshal's so you'll need to check images elsewhere.
Or try Corfe's
https://www.corfestone.com/search.php?search_query=kerb&x=0&y=0
Try the builders merchants on Tarran Way Pasture Rosd Moreton or Huws Gray at the side of Moreton Station