How do you get or make one of these other than the zapper?

I am pretty sure you can only get it if you had completed in the Blake Steele Excavation plot. >:

Jenni is right >: Although some people have been getting the little dino's in the Zapper so I guess those are the only two ways~

You might be able to find someone that can adopt one for you. Although that could be quite risky to do.