You're right, I just went out an looked at the 300 tdi. I don't know why they did that - the V8, the 200tdi, the 2.5 all use a spade, but the 300tdi has a post. Anyway, I suspect if you try one of those crimp connectors for splicing wires - that would fit. I don't think I have any here at the house, but I'll go look.
Found a blue one and it is too small, but I think a yellow will do the trick.