Where to get lightweight flexible coupling?

[sanddrag]

I know there are two or three threads on these couplings out there already but they are old and closed.

I need a flexible coupling that can withstand in the range of 500 in-lbs of torque. Something like McMaster #6408K17 but not made out of iron, maybe aluminum. I found McMaster #59985K5 which is aluminum but I have two concerns. Is a slotted disc type a good type to use? And it has no keyway and no through hole, do we mill a rounded keyway or do we bore through and broach?

This coupling needs to have a 1/2" bore in both sides, and needs to come keyed or be able to be keyed 1/8" Lightweight is a big priority. I looked in the LoveJoy PDF catalog for their jaw couplings and I see they make some aluminum ones but I have no idea where to get them. I checked all the usual places and even some not so usual places.

I see from the old threads that teams 968 and 45 have used CEC couplings but I can't find anything about them on MSCs online catalog or anywhere else.

Does what I need exist, or do we have to CNC out some aluminum ones?

Also, as far as the torque rating goes, how far over their rated torque can you push these things in a FIRST robot situation?

We need to order these really soon but I can't find what I need anywhere. Thanks in advance.