You can get these from a couple different places, but your best bet for variety is gonna be a cigar store. Don't let them charge you more than a couple bucks for any box. I have also found them in thrift stores.

Cigar boxes come in various levels of fortitude, from the humble paper box to the full-on wood box with a hasp. Get whatever you're comfortable with, knowing that you'll have to cut two notches out of the short sides to accommodate the neck. Use the 34" piece of hardwood itself to measure the notches out for a nice, tight fit. The book says to use a sharp utility knife to notch a paper box such as this one, and while I agree, there has to be an easier way to notch it cleanly. Anyway.

At this point, it should fit, but you won't be able to close the lid like you used to. Use the box itself to mark the width of wood to be removed, and the lid to mark the depth.

I used a mini hack saw and a flat head screwdriver to chisel out mine, and then a four-in-hand to file it down to the prescribed line. Yes, it took a while. No, I don't want to do the headstock the same way.

Now you need to remove wood in the same fashion, but from the 6" section marked 'headstock'. Use the 40mm M6 bolt as a depth guide. This bolt will sit right up against the 90-degree cut and serve as the nut. The strings will nest into the threads.

[No picture for this yet as I am waiting out covid to use my FIL's router.]