What route and where are you located? Someone is more likely to loan one to you than sell one to you. Those who have VGs very rarely part with them, and for good reason. Tom makes a quality, dependable product.
There is a route called Danger High Voltage on the north shore of Minnesota. They say a camalot 6 does quite cut it, for a section of the climb. Its probably the only place I would use it around here so I wasn't looking to buy new.
So far in my search to borrow something, my friends and I are at a loss.
I have exactly one VG12 in stock right now. I will have more VG9 cams in about a month.
The VG12 has the same size range as the #4 Big Bro. It has the advantage that it can be pushed up a crack. It has the disadvantage of being more complex to build, and it costs three times as much as the Big Bro.