I don't think you would find a PSU with that wattage for that system. It was not made to support high-end GPUs.
The T30 uses a Dell ONFX6T proprietary 290W PSU (175 mm x 36 mm x 454 mm) with an 4-pin and 8-pin ATX power connectors.
If you look at the label you will find the model #: AC290EM-01.