You can get more or less isolating tips most IEMs. For example, try going to
Comply's website and clicking "find tips for your earphone." That should work for common brands. Otherwise, you just need to know the bore size.
Foam tips will usually isolate better than silicone. To some extent, isolation will depend on the IEM itself, though. Depending on whether it has any vents and wear those vents are placed, what it's made of, and how deeply it fits.
If you're coming from Apple earbuds, I'm guessing most IEMs will be a significant step up in noise isolation. If max noise isolation is your #1 priority, though, you might also want to look at something from Etymotic or similar, where the IEM is inserted very deeply.