I think the "someone who brought it back" is Swiss Micros, which makes a compatible calculator (which they call DM-15) as well as other models in the same family. They say their chip that emulates the original cpu is quite a bit faster than the original.
HP themselves also briefly brought it back about a decade ago as a limited edition model that runs ~60 times faster than the original, running an emulator on an ARM microcontroller.
The HP store shows many of their remaining 7 (!) calculator models out of stock quite often. I'm not taking any bets on how long HP is going to make any calculators at all. I feel sad every time I visit their store...
They already stopped making any kind of graphing calculator, apparently.
HP ported their calculators to iPhone and Android apps. Most people who want an HP calc probably just use those now instead, except for the few who want the tactile feel of calculator buttons.
For the discerning STEM student/professional, 15c is the only relevant RPN emulator on mobile officially released by HP and it's an overpriced disappointment IMHO.
HP didn't even extend a courtesy reach-around for our CS/CpE brethren with 16c integration despite their $16.99! Even if you were in the market circa 2011 to pre-order one (or a few) 15c LE--which came with a copy of the desktop app--you'd still have to pony up even more for the mobile app!
On Android, I'd highly recommend skipping the "official" HP garbage and supporting CalcTastic Plus[1] for a mere $0.99. Even the free version makes the HP emulator look like a complete joke. I've been rolling with a 35s as workhorse since undergrad days, but couldn't care less if today's zombie HP literally disappeared from the market tomorrow.
I also want to mention the HP-45 iPad / iPhone app; it runs the exact microcode of the original on a VM. (My buddy was involved in this, and makes some $ - but I bought it and really really like it, and this isn't an ad, etc, etc.)
I have a 42S emulator running on my iPhone, but it really isn't the same as being able to press physical keys on a hardware device.
One of the charms of these devices was that they were built to last. ie: the keys were injection molded with two colors of plastic so they wouldn't wear down. So, while I still have a couple of working HP's from the 80's, I've been through a dozen or more mobile phones in about the same time...
They're called doubleshot key caps. The better mechanical keyboards also use this method. The HP-15C and others in that line were exceptionally well made, with the PCB for the keyboard being ultrasonically welded for rigidity.
I have actual 42S. The physical device lasts very well but the LCD fades out as it gets older. Right now mine does not have enough contrast to read it looking at it directly. You need to look it from downward angle and in perfect light.
Other than that this is the best calculator ever made.
At the time I bought my 48SX, I remember briefly considering a 42S. I had a lot of fun with the 48, but in retrospect, I'd have gotten more use out of the 42.
(But what I really regret is not having bought a 16C.)
Faster is not necessarily better here. My HP-12Cs have been going on their original batteries for more than 10 years each now, but I expect a faster processor would mean shorter battery life.
https://www.swissmicros.com