Reddit reviews Traveler's Company Traveler's Notebook Refill 013, Lightweight Blank Paper, 128 Pages

I feel like more stuff fits than you expect. It's just slightly shorter than US letter paper. This is a walkthrough on how to make a booklet but it also shows the difference between traveler's notebooks and US letter. You could make one sheet that's the right size to give you an idea of what you're looking at.

Dang! It sounds like you already have a great plan of action.

Here is the Midori planner insert. There are 215 pages of options on etsy. If you see something on etsy that is close but not perfect, you could message the seller and see if they'd adjust their layout to fit what you want. Some do printables and others will send you a finished notebook so make sure you read the description to know what you're getting. Here is a store selling what you described for your weekly as a printable. I'm not sure where you live but I know you can buy stuff in person at Kinokuniya.

If you do printables from etsy then you could add months, weeks, or whatever, on your preferred paper. I use a mix of knock off notebooks, midori notebooks, and booklets I've designed myself (One is for my hobbies and the other is a pokedex - neither are very fancy.)