There's no IEM in my opinion that exists that will do what you need for $100.
I've been using IEM's on stage and in the studio for about 5 years now and I've been though 7 different sets by various manufactures. I've researched them in depth for the last few months as well so hopefully I know what I'm getting on about.
What you really need (like me) are custom Future Sonics Ears. It's the most natural sounding IEM there is and the custom molds give you great isolation and great comfort. Marty and co. are great to work with too. Bad news is their $750.
The UM-1's are probably the most comfortable universals but they don't sound very good to me. Future Sonics EM-3's, or FS-1's can be had for around that price and can sound great but aren't good at either comfort or isolation. Atrios sound great right out of the box and more natural to me than armature based IEM's but once again aren't that great at anything else. And their $130 minimum. They are maybe my favorite sounding IEM and since you can't get there from here I highly recommend getting a pair from RoadDogOnline on Ebay. You can often "make an offer" of $130 and they'll accept it.
I'd really suggest bitting the bullet and going with a set of Livewire Customs for $250 if your ready to commit to using IEM's a lot. Customs are the answer for your comfort and isolation priorities. It's really no contest actually. Everything else will probably just "get you by" but eventually if your like me your gonna wind up buying a custom set anyway so you might just save yourself the buy-listen-sell-buy-listen-sell trouble. They sound good to. My favorite armature based IEM that I've tried. They come in at or way below their competitors price but they're customs where the others aren't. I don't think it gets any better unless you drop $750-$1100 on Future Sonics or UE customs.
Here's my rundown of IEM's I've tried:
Future Sonics EM-3's- Amazing deep punchy bass. Smooth sound, rolled off recessed highs. Need a pretty aggresive high shelving EQ. Not very comfortable at all. Not built well. $100ish.
Future Sonics FS-1's- Better highs than the EM-3's but not great highs. Same great bass, more comfortable. Not build well. $100ish they replaced the EM-3's.
Future Sonics Atrios's- Best sounding universal I ever tried. Serious punchy bass, smooth natural sound with nice clear high end. Mids are kinda recessed. A little EQ and they sound really, really good. Not build well, bad isolation and only reasonably comfortable. $140
Westone UM-1's- Sound pretty mediocre. Couldn't get the punch or sparkle I wanted out of them. Real comfortable and build well. Decent isolation. $150? I sent them back for UM-2's.
Westone UM-2's- Sound pretty good. Very good thumpy bass. Not punchy like the Future Sonics though. Very strong forward midrange with mellow not-very-shinny high end. Had a sibilance problem that I absolutely coudln't handle from a $250 IEM. Very comfortable, built well, good isolation. Sold them.
Shure E-2's- Sound pretty good. Good mids, pretty good bass. Mellow high end that needs EQ. Very uncomfortable to me. Built well. $150ish these days. In a pinch I'd buy a pair for the road.
Etymotics E4-S- Amazing High end. Good mids. One of the best sounding IEM's around by far. Hyper detailed. I wouldn't call them natural though. Lots of fan boys here for sure. I can't really blame them. If I didn't need the punch I'd be one too. I could not get any punch out of these what so ever and that killed them for me. Pretty comfortable although the cables were pretty microphonic. I hear they might have fixed that. Built well. $250ish
Livewires T1's- Sound better then the UM-2's I had for the same price. Good smooth deep bass but not nearly as punchy as the dynamic driver Future Sonics. Very good mids and extended somewhat shinny high end. Not as shinny and hyper detailed as the Ety's though. Built really well and no contest on comfort and isolation since their customs. Look for my review. John and co. are really great to deal with. $250
IEM's are expensive but they're getting better all the time. Finding the one with the right trade off of features is the key. There's not one that will do it all until you get up in the $700's. Not for us musicians anyway. If you you can't find it then I'd suggest a set of those high isolation full size cans that are build into safety phones they use at firing ranges and such. But once again, they're over your budget.