A place to source 16-bit heightmap stamps for the updated terrain editor?

This is not exactly a question about the new terrain system itself, but I figure many users here are using new brush/stamp system in 2018.3 so there is a chance someone with an answer stumbles upon this thread. Can someone point me to a good source of 16-bit brushes? I looked at Gaia, but it seems to be shipping with 8-bit .jpg stamp images that seem to be used only for preview purposes and packs the proper high quality stamp into a proprietary file format.