Try to contact the manufacturer directly, sometimes they share!
I asked manufacturer first but got no reply.
Sorry forgot to mention...
PS: Yesterday I received the
Epiphone Studio 15R schematics from Gibson Customer Service.
After checking I can confirm the PCB is identical to the wanted
Invask Invasion SG15R as I supposed, the Gibson/Epiphone is just missing one JRC4558 double OP amp and MIC-Level pot and input jack for MIC.