I have encountered a similar situation in UE5 while using a Thin Translucent Material for a sequence cinematic.
I have a HDRI backdrop that I wanted to use for lighting, however, I wanted a separate cubemap to be in the reflection of my glass bottle material.
Now, I am a noob, so I play around till I get something working, this very well may not be an efficient way of achieving this.
Still, I essentially have a Reflection vector multiplying with a fresnel, plugging into my emissive color. I also have a Specular parameter set to 0 (removing HDRI reflection).
This setup has allowed me to control the aggressiveness of my intended reflection (with BaseReflectFractionIn Param) and also blend the HDRIbackdrop (with Specular Param) if I want.