CSD can be downloaded on Cisco download site. Here is the path to download it from download center:
Downloads Home --> Products --> Security --> VPN and Endpoint Security Clients --> Cisco Secure Desktop
Hostscan is part of the package up until version 3.0 where it gets separated.
Here is more information for your reference:
http://www.cisco.com/en/US/docs/security/vpn_client/anyconnect/anyconnect31/administration/guide/ac05hostscanposture.html
And here is where to download Hostscan:
Downloads Home --> Products --> Security --> VPN and Endpoint Security Clients --> Cisco Hostscan
Hope that helps.