Just a note that i read here in the past. The soap dishes like you've got were referred to as dangerous because people grab the bar that is meant to be for wash clothes. You might be able to find a match that doesn't have the bar in case you are concerned about this safety issue.

Sounds like scale build-up. You can buy scale remover or use vinegar. You could use the same idea of soaking a towel in the scale remover or vinegar and leave it over night. I would use some old rag that you can just throw away and probably cotton would be best if you choose to use that scale remover which is kind of strong. Vinegar will probably not harm a cloth. This may take a few times to get it all. But if it's hard and sharp that would most likely be scale from your water. We have scale in our water and vinegar gets it off. It can also build up on the shower head and cause the water to not come out very good, you can put vinegar in a baggie and put it on the shower head and use some tape to hold it there over night. It will be clean in the morning!

Have you tried calling the Pottery Barn outlets to see if you can still get it from them. I know the Restoration Hardware outlets here have a lot of bath hardware/accessories, so I bet the Pottery Barn outlet would, too. If you don't know the item name/number, try using this website to go back in time. You just type in the web site address on the main page, and then go back a couple of years and click on one of the blue circles (you may have to select a few in order to get what you want). Good luck. And if you've never used that web site before, it's insane, I know. http://archive.org/web/web.php

More likely a real hardware store. They are usually about 1/4 inch wide to clean out mortar joints in brick. A big box might have them around the masonry/brick supplies. If you cannot find on a 1/4 inch cold chisel can be made to work, they are just harder to hit firmly.