I think that commercial session IPAs are indeed a rare thing. However it is absolutely possible to brew one yourself, and end up with a beer with the hop punch and mouthfeel of an IPA but in the 4-5% ABV range.
I have two kegged myself at the moment, they are one of my ideal hot weather beers, as they are hoppy and thirst quenching, but I can have one or two in the sun and not be laid out like I would if they were 7-8% beers.
I find that the mash hot with some adjuncts and add sugar in the kettle approach works very well for the style. A British base malt (GP does an excellent job), some flaked oats or barley for the body, a touch of crystal for color (4-8oz max), perhaps some honey malt, mash at 158 and a pound of turbinado in the kettle for an OG of 1.048.
Or if you can step mash then you can skip the kettle sugar and up the base malt a little to compensate. Give it an hour at 148, ramp to 154 and hold for 15-20 minutes then mash out and boil.
A small addition of columbus (NMT 15g) for FWH, then blast it like you would any other IPA, 3-4 ounces at FO, 3-4 ounces in the whirlpool then a generous hand with the dry hops.