In the Ear Headsets
Currently there are five choices that I have seen.
In ascending order of price, there is the Plantronics MS200 at about $130, which replaced their MS30-2 that did fit tightly in the ear canal. Each purchased headset came with 6 earpieces so that you could pick the best fit. They also make the MS20-2 that fits in the ear and is held by a clip that goes over your head. Pilots take the headclamp off and clip the headset onto the arm of their eyeglasses.
Next is the Quiet Technology Halo priced at $359. Like the older Plantronics MS30, it has an earpiece that fits in your ear tightly.
Clarity Aloft and Lightspeed Mach 1 both retail for $525 and are similar with the exception that Clarity Aloft has two earpieces which engage both ears.
The last choice is from Phonak in Switzerland. These folks make many many hearing aids and have just entered the aviation headset market with their FreeCom 7000 priced at $1357. I believe that it features Active Noise Reduction rather than Passive as is the case with the first four devices.