Perhaps the most important source for data on language acquisition by children learning a variety of languages is the Child Language Data Exchange System (Childes). This includes audio and video recordings, as well as transcriptions, of the speech of children.
The classic article referred to in Question 4 of Chapter 12 (p. 000) is freely available, Berko (1958). The full set of wug prompts used to be available on the internet, but now can be purchased in the form of a book:
Gleason, J. B. (2019), The WUG test, Cambridge (Mass) and Wagener (S.C.): Larchwood Press.
Linguistics: An Introduction > Student Resources > Chapter 12
