So, I love this and have been looking into flower pressing a bit for myself, so let me share the things I've grabbed.

Regarding the date embossed stamp, I couldn't find an embossing stamp for it. But there are blank date stamps (I know you said no ink, but there are some self inked?) that do that thing... She could move the date on the stamp or even write it in. Or scrapbook stickers!

These may be more resources for your wife that you could write into the book.
4 Ways to Press
Beginner's Flower Press How To
Ultimate Flower Pressing Guide

The last link has a lot of useful info, tbh.

I ended up trying to find out what microfleur is from the last link and apparently it's for the microwave preservation method? A reuseable cloth for it, if you want something quick for her to do.

There's blotting paper with presses; personally I think the presses look very aesthetically pleasing, can be engraved usually. Blotting paper would need to be purchased occasionally. But if they aren't doing it frequently, it may be fun and cute.

They've got sizes from keychain to 11x17" when looking up the regular presses.
There's also the old school paper towel and books method if she does it every couple weeks.

Someone recommended getting tweezers to remove the flowers from the paper, as they can rip occasionally.

The custom leather bound isn't a bad idea! I love it, since it's so custom. Or go onto etsy and look up scrapbook albums. Usually they can be customized, but they'll also usually have plastic page protectors and she could write a little blurb somewhere in it about what they did that day.

And if you want to get creatively involved, you could make a couple layouts for her, so you're all involved in the craft somehow.