Check out z39.50, you can use it to search and pull data from most national and university library catalogs. But also be prepared for some code archaeology along the way, as the protocol is around 50 years old.

https://en.wikipedia.org/wiki/Z39.50 https://z-brary.com/ https://github.com/asl2/PyZ3950/blob/master/PyZ3950/zoom.py