Are these mounting brackets easy to find?

I emailed Tripplite to see if they sold them separately. Maybe someone here knows. Can I buy these mounting brackets shown on the right and left side of this (SMART500RT1U) 1U rackmount battery backup https://i.imgur.com/tBXqNoq.jpg

I need 8 of them. Worst case scenerio I'll bend some sheet metal and drill holes in it. But I really don't want to go that route.

Here is a better picture of the bracket: https://i.imgur.com/Vwl9sEl.jpg