Is the adapter piece the cap on outside end of the earpiece?

The adapter slips on over where the flanged ear sleeve normally would be.
Twist off the flanged sleeve and the adapter is supposed to slip on and make
the thing maybe another .025" larger in diameter so if fits as an
interference fit inside the Sensaphonics. It isn't much and you might be
able to wrap some narrow electrical tape to build up the diameter until they
get you the adapter. The adapter may have a lip on it too to help it seat
into the Sensaphonic's sleeve. Still don't have mine to compare it to.

Nothing looks bulbous and you cannot tell it once they are in your ears.
They are made of a really soft clear silicon so they fit pretty well. You
may want to chew some chewing gum while they are making the impressions so
the mold stuff will form well to your canal. Ask you hearing aid guy about
this.

Supposedly some of the non-silicon mold impression stuff shrinks in transit
to Sensaphonics and they want you to have them made with the silicon
impression stuff which doesn't shrink as much - else they will fit a bit
tight once made and may irritate you. Mail them off quick.

Fwiw, I also got a custom molded pair at a motorcycle show from some vendor.
They were a dual-driver type and sound similar to the Shures I have but with
a bit more treble and lot more bass than the Etymotics. Cost at the show
was around $350 and they came from Westone (westone.com).

I just found the vendor's website:
http://www.myearplugz.com/Event_Dates_Static.htm

They are a lot more expensive on the Westone website than they were at the
show by maybe $200. Cords exited differently too, straight down for
helmets, where the Westone series goes up over the ear. They are a bit
harder silicon than the Sensaphonics and much larger in size as they fill
more of the outer ear than the Sensaphonics. The exit port to your eardrum
is also smaller and more circular than the Sensaphonic's which is larger and
more oval in shape. I'd say the Sensaphonic's is more polished in
appearance too.

B~