Use a single N channel J-fet. (Most popular type)
Tie the Gate to GND, tie the Drain from anywhere 2.8v to 25v/45v/75v (depends on Jfet's max voltage, rare 250v Jfets do exist) and the Source pin is the output which will be a regulated ~2.8v.
(Output voltage is the J-fet's ~VGs cuttoff voltage listed in it's data sheet)
Some J-fets will give you 1.2v, others as high as 7.5v. The output voltage play from J-fet to J-fet of the same part number is around +/- 0.1v so long as you keep using the same manufacturer.
The quiescent current on the Gate's GND connection will be in the
nanoamp range. You will not find a regulator which will consume less current than this. A simple 1nf-100nf cap from output to Gnd will make the output clean. Do not draw more than a few ma, or you will loose regulation. The dropout voltage is ~0v! Low noise audiophile grade voltage reference.
Examples:
Digikey overpriced N-JFets