I have a lops camera that need frustums built from the exact settings input in them for sensor size and focal length.

I haven't found any good information on successfully getting the transform of a lops camera into sops space to build something from it.

Is there a node, vex function or technique to doing this with Solaris as of 19.5.368?

I don't think there is a direct way to sample LOP camera from SOPs (except from using Python)

but indirectly you can create LOP Import Camera Object (either in/obj or in any Object Network) and then sample it from SOPs like regular object camera