Secondary connection to hotspot

My openwrt device does routing only. When my wan goes down, I grab my gl inet travel router and spin up a backup network to continue working from.

My router has WiFi, but it is not used at all normally. I have a deco system handling that.

My goal would be to connect the main router to the same hotspot that the travel router connects to to minimize the impact to the rest of my house.

I have found bits and pieces of what to do by searching, but nothing definitive and that has worked.

Can anyone point me in the right direction, please and thank you!