B1C5
This post is going to read like an ad, but it is not.
Calligraphr
Calligraphr is an amazing website that let me create my own handwriting fonts. I did this for Kartik's handwriting in the map last chapter, and for B's handwriting in the note in this chapter.

It would have been somewhat easier to just write the note on a paper and scan that in as an image, but making my own font sounded so cool I couldn't resist. (This also makes changing the text later easy, but I mostly did it because of the coolness factor.)
For USD $16, Calligraphr will let me make as many fonts as I want for three months. The process is so easy that I'm seriously tempted to add a new handwriting to each chapter.
First, I print out a few templates and fill them in with the handwriting I want.

Then, I scan in the templates, upload them to the website, and clean up the resulting font a bit. Literally five minutes later, I have my own font.

One thing I love about this is that, as you can see in the last line ("apple flabby..."), the same letter can have different forms (e.g., the two p's in "apple" look different from each other). This makes the resulting words seem more handwritten.
Pentel
Pentel is a Japanese company that makes pens, pencils, and other stationery items. I bought two mechanical pencils from them for ~$5 more than a decade ago, and those pencils still work and bring me so much joy every time I use them. I feel a little bad at how sturdy and functional these pencils are, because if they broke more easily, I'd have bought more of them by now. This creates perverse incentives for the company, and I feel like I should somehow reward the company for making products that are so good, even though they could maximize their short-term profits by making worse products. So, in lieu of buying more pencils from them, I'm spreading the word about them.
When Lisa refers to Paul's "special Japanese red ink pen", in my mind, that's a Pentel red pen. The color I use for circling Tina's name a few paragraphs later comes from that pen's packaging (#dd3d36).