Many years ago I purchased some Westone ES2's, as well as some custom fitted earplugs. The fit on both was never fantastic (turns out I should have had my mouth wide open while doing the fitting, the audiologist disagreed, I didn't know better at the time), but I lived with it. Over time the fit became worse, and after a few years the monitors were pretty much unusable. The earplugs were a bit better, but still didn't work like they should. The cost of getting them redone was way too much, so I moved on.
Well, fast forward to last week when I was talking to someone about casting molds of model parts, and he mentioned that mixing silicone and corn starch together gives you a substance that can be molded like clay, and will completely setup all the way through in a short period of time (unlike using just silicone, which cures from the outside in, and takes a long time if it's not very thin). I experimented with it, and realized that once you mix equal parts corn starch and silicone, and let it sit for about 10 minutes or so, it has the same consistency as those soft beezwax earplugs. So, I put a little vasaline in my ears, and shoved a chunk of the stuff in (not very deep, mainly in the outer ear). Well, after leaving it in there for 30 minutes and then letting it sit on the table for a day, I had some custom made earplugs that cost me all of about 50 cents.
This got me to thinking about my custom molded plugs and monitors that didn't fit anymore. I made a little of the silicone mixture, and wrapped a thin layer around the stem of the earplugs that goes into the ear. I put the earplugs in my ears, let things setup, and now they fit right! I did the same thing with the monitors, and now they fit again as well! The best part of this is that the silicone mixture is flexible when set, and can be peeled or cut off later on if I ever need to redo the seal.
So, If there's anyone out there who has some custom fit earpieces that don't fit anymore due to shrinking, or never fit exactly right in the first place, this is worth trying. The materials are super cheap, and it's pretty easy to do. Now if only Westone didn't charge close to $50 for a replacement cable, I'd be a happy camper.