The great thing about headphone audio nowadays (as opposed to just 10 years ago) is there are quite a few low cost options that sound great. Unfortunately they're not well known unless you do some research.
That said, if you want top-tier audio out of something extremely portable that isolates to a degree, I cannot recommend Sennheiser's IE800 highly enough. I've spent many a kilobuck over the past 15 years and these are some of my favs. Not cheap at $800 retail (used in the $500-600 area), but totally worth it if you listen often while working. I have other IEMs that cost 2-3x as much and prefer these.
Most of time I use these in conjunction w/ Roon audio player and a Tidal sub straight out of the headphone port of my 13 rMBP - total audiophile bliss.
I wonder if they use the same speaker/driver as the porta pros?
All of mine died really fast though! The cable is so thin and the connector tail bit so short and inflexible, that plugging them into a phone and putting the phone in a trouser pocket daily is a 6-month death sentence tops.
They leak sound like crazy and look like they came out of a time machine from the 1980's. But they're cheap and they sound great.