Sourcing low esr caps

You could use multiple smaller-value caps in parallel and make the ESR, and the ESL, as low as you want, especially if you mount them on a thin two-sided PCB (with unbroken power and ground planes).

Or, maybe two cheaper caps in parallel could have lower ESR than one expensive cap of twice the capacitance value.

Why do you need low ESR? Is it so they can handle a lot of ripple current without getting too hot? Or is it to make a PSU have low output impedance?