Yes I think it's awful when schools hand out licences too. Much better to quietly tell a child that they can use pen from now on. Unfortunately, the recipients are often so proud that it does become a bigger deal than the teacher might want.
I wouldn't want to recommend a book to you in case it was the wrong one for your school, but then I don't think you actually need to spend any money. Ask the school for a sheet showing their preferred handwriting style - they'll easily be able to do this, and then you need only practise the letter formation and joins. If they use specific handwriting workbooks, ask if you can have one or offer to buy one from them (I've given these to parents before now).
Yes lots of people have said to give everyone a pen but it wouldn't work, it really wouldn't, and I am not in the game of making children sad. I have seen children writing 10x slower when using a pen, crossing out to the point their work is illegible, crying because they've made mistakes that are now permanent and can't be erased, letters so big they take up two or three lines on the page. Some children are, for now, doing better work with a pencil, whether they realise it or not.
The coolest kid in my class is the one who happily uses a pencil and loudly tells everyone they're mad to write in pen. He says they're always running out and you can't erase your writing. He does a hard sell on pencil that has obviously come from his mum.