Anyone that has purchased the FlexRIO MDK can access the latest copy of the MDK by going to the FlexRIO MDK community group. That group has a document titled "How to Download the latest copy of the NI FlexRIO MDK" that will always have a link to the latest version of the MDK.
https://decibel.ni.com/content/groups/flexriomdk
Note that the group is invite only. If you do not have an invitation please contact the FlexRIO MDK email group.