These are no longer publicly available on the website do to them being deprecated and not supported. You can file a support ticket or ask your Account Manager to get a specific version to you for testing.
Hm. Also having issues trying to find the DBConnect v1 download. I happen to have v1.1.5 in my downloads directory, but 1.2.2 was the latest 1.x version. I'm trying asking around on the Splunk Usergroups slack.