The very early T5500 MB D883f had active SB cooling. 0G422G is the part#. Prices vary wildly on this item and other MB wont have the 4 pin header to run the fan.
Here's one from china with a relaistic price.
[USD 10.40] DELLT5500 motherboard chip fan t7500 motherboard chip fan 0g422g North and South Bridge fan - Wholesale from China online shopping | Buy asian products online from the best shoping agent - ChinaHao.com
buy DELLT5500 motherboard chip fan t7500 motherboard chip fan 0g422g North and South Bridge fan at taobao agent Computer hardware monitors computer peripheralswww.chinahao.com
Actually the issue is not getting a decent SouthBridge Cooler.
The issue is that the SouthBridge Cooler is coming in way of Graphics Card, no matter in which of the two pcie X16 slot Graphics-card is being mounted.
Because all mid range gaming Graphics Card are at least Dual Slot Wide and even the mini version is at least 17 cm long.
Because there is very little distance between X16 Slots and the SB area.