Part number 99610644700Source-mentioned candidate. Verify fitment and availability independently.
Cited source accounts
The coolant cap is P/N 996.106.447.00. It's definitely not coming from the cap and I can't find any signs of a leak from up top. I'd have to start removing things to pinpoint it. Honestly, with how old I believe it is, I wouldn't mind replacing it anyway.
Replace the coolant tank cap
This is a source reference. Confirm exact model applicability in the original material.