Can you name some sort of item or product which weighs circa 1 kilo?

Bag of sugar

As a benchmark, not perfectly accurate, a litre carton of milk or a litre carton of most liquids such as wine, water, juice etc will be very close to 1 kg. A standard bag of sugar is 1 kg and some bags of flour are 1 kg although they do differ.

In the United Kingdom and europe a bag of sugar.In USA a bag of sugar is probably quite close to the same.Another is a litre of soft drink. or two 500ml cans of lager.(not that I would even suggest that a Yahoo customer would drink spirituous liquor,but you might know some benighted sinner that is not so particular,and perhaps you could try a couple of cans for weight,

How about 1 litre of water or 3 cans of coke

1 Litre of water is exactly 1 kilo but take in consideration the weight of the container.

A quart of milk (about 5% shy of a kilogram... probably pretty well spot on if you include the container).