The master site for pattern language is at https://www.patternlanguage.com/ . The web site is a good archive for Christopher Alexander’s papers – some unpublished – and pointers to the books.
On the Internet Archive, there’s a copy of A Pattern Language at https://archive.org/details/patternlanguage00chri that can be borrowed for 14 days. There also seems to be another version labelled as “Ecological Building” that could be less restrictive at https://archive.org/details/eb_A_Pattern_Language/ . However, since the patterns are often used non-linearly, a sequential text may not be the best presentation for synthesizing patterns into a design.
One site that was really great at providing links to “higher order” and “lower order” patterns was on the Jacana House site. It now seems to be offline, but since it seems to have been coded in days of simpler HTML, the version archived at https://web.archive.org/web/20190906082635/http://www.jacana.plus.com/pattern/P0.htm still surfs well.
On a more modern infrastructure is a collection that might have been the impetus for a set of New Patterns, at https://patterns-dev.github.io/patterns/newpat/newpat0/new-patterns-introduction.htm . This was dated 2012, from Theo Armour.
Many of the constraints on electronic publishing of A Pattern Language come from original agreements on the 1977 edition from Oxford University Press. From that site, there’s a “Google Preview” that is searchable, if you want to search and view specific pages.