you can get various rubber from vendors but the hyperfirm is a close knit formula known only to a handfull of people.
I highly suggest if you plan to delve into any rubber fabrication, you learn hands on from someone who knows what they are doing. Its highly toxic, can burn and discolor your skin not to mention what it can do to your lungs, eyes, nose... You need extreme ventilation for rubber work if your looking to use it at home. The fumes are also highly flamable. Fun times.
If you are thinking of going it alone, at the least, do some research with the vendor, always test with a spare mold (not the one your looking to make parts from) because you will probly ruin the first mold you use it on and the wallet will get much lighter.
You also need to take into account internal armatures if its anything larger than a TV remote control. It gets complicated.