you have the KarKraft kit or the CDC kit? CDC you get from them, KarKraft you get from a junkyard or Ford.
If you're not sure post a pic, I've had both on the car so I'll figure it out for you... I just need to see the front of the shaker where the tube would connect.
There used to be a place called fordpartsnetwork.com that sold Ford Mustang parts, they had all of the Mach 1 shaker parts listed on their website. It seems they had to change names due to Ford's licensing lawsuits, so I don't know their new name. One option is to find their new name - a goggle search might turn it up.
Another place to try is below, but you'll have to dig up the part numbers. If you do a search, those have been posted here before, but its been a while. You may have to go back a couple years.
since its a CDC part, your best bet is to call them. I know they have a ton going on this time of year. I'd give you a direct contact number but I don't think they are co-sponsoring my car any more since I um switched shakers, so I don't think I can do that