Replacement Sink for Vanity unit

Several years ago, I made a vanity unit which housed an inexpensive sink
unit which was oval shaped and about 17 or 18 inches wide.

I now need to replace that sink but seem unable to find a similar sized sink
for sale.

The original one is made of GRP or plastic (hard to tell) and I think was
bought from PAYLESS (as was)

This is only for use in a spare bedroom so a similar construction (ie GRP
instead of ceramic etc) will suffice


Can anyone suggest a place to try looking?

TIA