Ceramic tiles are often created as part of a company line. These lines, much like a clothing line, go in and out of production as the company sees fit. This can sometimes create a frustrating scenario when trying to find old ceramic tiles that match those you need to replace.
Identify the tile manufacturer. Look for any distinguishing marks on the tiles or unique characteristics that could provide clues. You can also try showing a piece of the tile to a tile retailer to see if they recognise the manufacturer.
Once the tile manufacturer is identified, contact them to see if they still produce the piece or have leftover tiles from the line.
If the manufacturer no longer makes the tile, ask them for a list of stores they distribute their products to. Contact the stores from this list to see if they have any of the tile left.
Contact an antique tile dealer who might be able to help you find that specific tile on the market.
If the tile is untraceable or nonexistent, use an alternate tile with a coordinating colour or pattern in place of the tile you were originally searching for.