I dont have a lot of experiance with this equipment but we did have the exact same drive go bad on a Garaventa. In my area Garaventa will only sell parts to a dealer so I bought the very same drive though Galco electronics
http://www.galco.com/buy/KB-Electronics/KBVF-26D. You can find these drives other places as well but my company just happend to have an account with Galco and they had one in stock. One tip though, these drives are set up by Garaventa at the factory so when you get the new drive anywhere else you need to set the adjustment pots to exactly where the old drive's pots are set. one of our mechanics found out the hard way when he threw the new drive in and it immeadiatly ran itself into the overhead.