Our first TT was a Coachmen Catalina 20RD. It had the same mouse hole that you push the cord into. On the 20RD, the box is just below a small exterior storage compartment at the left rear of the TT. When we bought it, we asked the dealer to make the box accessible in case the cord ever got hung up. It didn't take long to find pushing in the cord was a bother.
I ended up converting to a detachable Marinco power cord and inlet. The first pic shows a 1/8" thick HDPE cutting board that I got at a dollar store. Since the hole through the TT for the mouse hole cover was larger than the power inlet, I cut a donut shaped piece of the HDPE and mounted the inlet on that. I bought the round style inlet and cord on ebay for cheap. The complete kits and cord can be expensive and you don't need all parts like the outlet box. Along with a tube of RV caulk, the total cost was around $120.
If you want to mount the new outlet where the existing mouse hole is, you will find that both the round and square style inlets are smaller than the hole in the side of your TT.
The box for the power cord ended making a good storage spot for spares and things that don't ever get used much.
FWIW, the collars on the shore power cord connector come in two types, a threaded one and an 1/8 turn type. I've found that the threaded type can be a bit of a pain to thread on, while the 1/8 turn one is much nicer.


