You can find the twin levers at PFM brakes.com...Or you can just call & speak to Wal. 011-44-1624-845245. They weren't a good fit for me, but I'm sure my hand is smaller than your friends'.

 

Thanks Gypsy Lady... That's exactly the setup i was looking for... Also thanks for all the other replies...

 

I do not remember who said it but he was a MotoGP world champion.
When answering a question about rear brakes he replied: I never touched the damn thing.

The truth is if you ride fast and are hard on brakes the rear brake counts for nothing. There are a few exceptions like braking hard while riding two-up or emergency braking on the wet or emergency braking in the middle of a fast curve.

Now, if you do not ride on the limits, why do you need it?

 

how about rigging up a early ironhead rear brake lever, it is on the opposite side.. the brake and shifter would both be on the same side, but?? you don't do both at the same time anyway.. i had a bike that had both on the right side for a while..