Where to buy metal grills for custom cabinet door?

Good morning.

I am moving into a new condo and am building a semi-custom cabinet setup for my audio equipment. I'll be buying some used normal cabinets, removing the doors and building the new ones. I would like to use the metal grate-style doors that allow heat exchange but still hide most of the inside.

Any ideas about how I can DIY these doors, ie, where can I buy the metal grate style inserts? (think "Salamander" equipment doors, but a lot cheaper. For a specific example, google "salamander style 221.").

Any and all help is much appreciated.
You can try to find the metal grills that are used for radiator enclosures. They come in many different designs, and obviously designed to ventilate.