Now, all you need to load is the +5V line and maybe the +12V line. About 1A on the former and 200mA on the latter. Try using a 6V 6W bulb between the +5V pin and ground (it doesn't matter which ground pin you use) and a 12V 2W (or 2.2W, which is more common in the UK) bulb between the +12V pin and ground. The latter is a common car bulb, and the former should be available from a car shop that still supplies parts for old vehicles (or maybe a motorbike shop?)