FIAT Ducato gear knob
Yes, it's a trifle bemusing when it 'comes orf in yer 'and' and that spring pings away into the nether regions of your vehicle, isn't it?
To get a replacement, you bimble along to your local FIAT dealership's parts department, slap the broken one on the counter and say "One of those, please!" The guy then shuffles off, as they do, comes back eventually with the box, regards his computer and says "That'll be £25.23." You say "HOW MUCH!! Mumble mumble grizzle, oh soddit... pay." You convey your precious cargo back to your vehicle, fit the spring, and gently but firmly biff the knob on to the gear lever with a rubber mallet.
This information goes back to 1st May 2007, and so far it has stayed put.