Well, I had two of these and I lost them both. One on a plane. Another in a hotel. I loved these things for the fit and the sound. So time to figure out what to get. Ive tried lots of headphones and they are OK, but time to figure out what to get next. Personally, I've found the fit is really important and love the Etymotic three flang (they work with any 3mm barrel).
First in-ear is just wonderful on planes with isolation and small size. Joker has the most amazing review set of 295 IEMs and counting and analyzing those things that are scoring 9+ in sound, leads to a easy analysis with the high values being trying to get a sound score above 9 and a value score above 9, so here are the ones that hit this:

• (Joker lists as 2B23) V-sonic VC1000. $125 on ebay. Sound score 9.2 and Value score of 9.5 (and that was assuming a$137) price.  It is based on the TWFK dual balanced amrature from Knowles  as is the Fischer Audio DBA-02 mkII and Vsonic GR01. Ebay has it for $125, so quite a deal. • V-Sonic uses 4mm tip. You use it with the MEElectronics M6 Bi-flange tips (TS3-DF-35-CL) as they recommend. • 2A12 Fischer Audio DBA-2 or Brainwavz B2 are the same.$130. The mkII is nicer construction but is \$200. Etymotic ER38-14F Foam 10 Pack is the recommended ear tips.