Yeah, bgalizio et al have it. Etymotic is the only group I know that does shells that can be used with IEMs and the standard sound plugs.
can you elaborate on that set-up? sounds great but what's the cost for it all?
Last time I had impressions taken I asked what the entire setup runs and they said $225 gets you 2 molds (L/R), and 2 sets of filters (I picked -15db and -25db) and covered the doctor visit. You might consider getting 2 impressions done in a single visit (not $450, but somewhere around $240) and then ship one set an IEM maker that does custom units and one set to a lab that does the ety-style shells for use with the filter buttons. Some labs will do both, like Westone (so you'd only need one set of impressions), some do just one or the other. Depends on what IEMs you want.
On the earplug set, just make sure everything goes past the second bend in the ear canal when you get them back. Likely to be the same on the IEM set, but not always (e.g. the Westone UM3x adaptors are designed to only go past the 1st bend, but their ES3x IEMs go past the second, small quirk).