Try looking for mine-related assets. Many of the buildings and equipment used at mines are similar to what quarries use. There are also things like 3D piles of ballast, which are just processed rock after all, and could be used to decorate a quarry.
Here's something I cobbled up using various assets from Ben Dorsey and Shortline (Linda). Also look for those assets that begin with YR these are wawasoo's IOI Mill and TS Shed assets. I used these on my Gloucester Terminal route in addition to those shown below, but don't have a screen shot yet of the operation.
Just a thought
You could turn this into a quarry if you want too
Ridge Colliery by changing the textures
includesdrag lines
drill rigs
loading areas
conveyors
colliery area covers 6 boards