Transformer for Flyback power supply
Sourcing a transformer a major challenge/headache during the design of an isolated power supply.  The more power is required, the harder it is to find an off-the-shelf magnetic.  Majority of the power supply transformers are batch-built.

Usually magnetics manufacturers' web sites have better search/filtering tools than distributors like DigiKey and Mouser.  Here are my go-to places for shopping for off-the-shelf magnetics:


Pulse Electronics
Coilcraft
Würth
the supplier listed in the BOM of the reference design


Lead times may be long too.