f5.saas_idp.v.1.0.0rc1

good question, unable to find anything myself. some iApps have previous version folders, but certainly not all. the code share https://devcentral.f5.com/codeshare/saas-federation-iapp links to the official download site.

but are you sure you need the older version? the newer support v12, but that doesn't mean it doesn't support v11. readme.txt says: Applicable BIG-IP versions: 11.2 - 12.1

if it really doesn't work i would certainly also contact support, it is in their bundle so if it really doesn't work they might be able to get you the old one.