The part number for the 3 pin extension socket that will plug into the 435VFS15 is -
438S15
Please go to the following links below and check under the Documentation Tab for more information.
Australia - https://www.clipsal.com/products/detail?CatNo=438S15&itemno=438S15-TR&backto=/search?q&tab-document-1=0
New Zealand - https://www.pdl.co.nz/products/detail?CatNo=438S15&itemno=438S15-TR&backto=/search?q&tab-document-1=0