Sorry for the delay - a little bit of an accident last night. Here’s the links to download the X1 & X2 certs and the intermediate leaf cert.
LE Root CA Certificates (PEM format):
ISRG Root X1
https://letsencrypt.org/certs/isrgrootx1.pem
ISRG Root X2
https://letsencrypt.org/certs/isrg-root-x2.pem
Intermediate Certificate (PEM format):
Let’s Encrypt R3
https://letsencrypt.org/certs/lets-encrypt-r3.pem