There has been no way found to get a MAK after the official TiVo service was discontinued. A MAK was obtained by registering on the TiVo server.
The only way to get a TiVo now is to buy one already enabled.
Also should you do a Clear and delete all you will loose your MAK permanently.
This also means that if you want to protect your MAK from a hard drive failure you need to image you drive when it is functional and load a new drive with that image.