I don't think those motor mounts are made specifically for converting the NTC3. Most of those look like the person used motor mounts from some other electric TC's and drilled the chassis out to make mounting holes for them. Shouldn't be too difficult to do, just need to figure out which motor mount will be a good fit.
Here are a few examples, not sure if they will actually work, but you get the idea:
http://www.amainhobbies.com/product_...ho-Motor-Mount
http://www.amainhobbies.com/product_...es-Motor-Mount
http://www.amainhobbies.com/product_...ic-Motor-Mount
You could also look into using the RC-Monster Revo mount as mentioned, or one of the Tekno motor mounts like this:
http://www.amainhobbies.com/product_...a-Novak-Motors
For a battery tray the RC-Monster CRT.5 tray is a good fit for most standard 2S hardcase packs. I am using one in my Diggity Designs XLR8 electric TC3.