1.5 liter Hawkins Classic pressure cooker = 930 grams = 2 lb 0.8 oz.
I'll have to dig out my 2L to weigh it, but it is only a little heavier.
There are non-structural plastic handles that could be removed that would save a few ounces, but you might need to gloves if the handles get hot. I think if you attacked the metal parts carefully with a grinder or file you might save a little more weight before compromising the structural integrity.
I've never had the Hawkins 3L.
You can sometimes find these in Indian grocery stores. Some of the other brands just don't seem to work as well. Hawkins also makes stainless steel cookers (heavier) of the same design and the Futura, hard anodized aluminum with a thick base (heavier). You want the 'Classic' aluminum. For home use, I've had Presto pressure cookers and another design similar to the GSI and I just like these Hawkins pressure cookers better. I use them frequently at home.
If you ever come across a 1 liter aluminum pressure cooker try to weigh it. I've seen, and lost, a reference to a 1 lb cooker which would be wonderful for me.
The standard is to fill the pressure cooker 2/3 full, so the 1.5 liter will actually cook about 1 liter of volume which should work for 2 people. If you're careful you can go a little fuller than 2/3.