This brown window crank is typical of what's available in the aftermarket and uses a metal rivet to secure the knob to the main part of the handle.  These are inexpensive enough to consider tossing an extra in your glove box! 

The upside is that they match the tan Vanagon interior very nicely.

One per front door.

Click here to purchase some new brown door window crank buffers.

Or click here for a brown window winder crank one and done solution!

Ref ID: 321837581A