I have the same Duplo Train that Pieterjan posted a picture and video of in September ('Old Lego duplo train not working on batteries'). In my case, it is clear that the battery connectors are corroded due to leaked batteries, and some have snapped as I removed them to clean them. Any idea where I might be able to buy replacements?
Considering that the contacts seem to be made specifically for this model of Duplo Train, I think an exact fitting off-the-shelf version likely doesn't exist. You could buy sheet metal of the same material and thickness, then try to cut and bend it to the right shape - or buy another (possibly otherwise broken) Duplo Train of the same type (or in red) to scavenge the connectors in used but official condition.