Where can I get these from (and dont say the USA!)

https://www.chatsworth.com/en-us/products/racks-cable-management/accessories/shelves/16-d-(410-mm)-low-profile-shelf

basically what we wont to do is to add deeper switches into wall mounted open racks.  The issue is that the current racks are only 300mm (ish) deep and the switches we need to put in are 450mm (ish) so these shelfs will allow the switch to site out further (which isnt an issue as there is lots of sapce out the front).  We can't replace teh current frames