Yes, there is a .dmg Here is the link:
AdobeFlashPlayer_21_a_install-4.dmg
The -4 indicates you've downloaded the file several times. Please do the following:
- Launch Disk Utility (/Applications/Utilities/Disk Utility.app) and unmount any Flash Player installers that have been mounted. If you don't have the option to unmount an item, restarting the computer will unmount it automatically.
- Delete all Flash Player installer files you've downloaded, empty them from the trash as well
- Download the installer from get.adobe.com/flashplayer
- Launch the installer - does it work?
if it behaves the same, please try the offline installer posted at the bottom of the Installation problems | Flash Player | Mac page in the 'Still having problems' section.