If your camera has the stud connection , I think the Mamiya RB 67 Strap Might Fit. You could also check out the Optech Superpro Strap that comes in two fitting styles of different sizes A and B, or even the Blad strap
If your camera has lugs, I seem to remember that Mamiya made a fitting to snap onto the lug that allowed you to fit any camera strap to a 330. This web address will take you to the older cameras section of the Mamiya user's forum.
If the link doesn't work, go to mamiya.com and wade your way through the menus to the user's forum and click on older Mamiya Cameras.
This Mamiya-sponsored web site is a very deep resource for the older tlr cameras.These guys are REAL fans of the 330 and such. Leave a message there and someone will have a comprehensive answer for you.
I have a C330S and C220F that use the lugs. OpTech makes one of their comfort straps with the proper lugs. Also, the strap for the RZ will also fit, I have one. They're really nice because they're so secure!