Advice needed: Rear Fog Light with low AND high beams installation

Dear Prius owners,

I am in desperate need of an expert advice for the modification that is brought upon me by EU regulations: I need to install the aftermarket rear fog light on my US-market 2014 Prius.

I've found enormous help in just reading the forum and was halfway through the installation, but the problem arises: I need to make sure that the rear fog light's switcher is powered only when low OR high beam is on.

Unfortunately, the two nests for low beams in fuse box are empty, there are only two fuses for high beams, but it is not enough for me eventually I need to find the location of a relay that is powered only when low or high beams are on. I thought of splicing into 2 sources of power - to low beam power wire and to high beam fuse, but it seems wrong, and also I assume that then the rear fog light would blink while switching between low and high beam lights.

I am pretty sure that I saw this relay on the scheme of the engine bay, somewhere closer to the windshield, but I cannot find this scheme now, maybe someone has it at hand?

Anyways, would appreciate any advice!