Hi John,
If you haven't come across them yet, check out the digmesa nano http://www.digmesa.com/nano-family/
Up to 50000 pulses/l
Exists in a PP, a brass and a stainless steel version.
I propose it be tested for espresso AND relatively short time spans, but memories of the dark brown liquid out of a MrCoffee-type device with heated glass-pot at a place I worked at do haunt me. And the cleaning....