Does anyone know if the Dell Optiplex 990 desktop form-factor has a riser card available? I'm looking for a x16 PCI-Express full-height slot. If so, what is the part number?

One was available for the Optiplex 960 but it doesn't look like it will fit the 990 due to the fact that the slot next to the x16 slot is PCI Express and not PCI.