For Middletown, Newport and the rest of those island towns, there never was much of a hoppy shop presence. Back in the mid 80's when I was in that area, the only hobby shop was in Newport itself on what of the back cobblestone streets but that had closed up when I was there.
I had found references to a Newport Hobby House, but there web page does not exist. Here. Their addressand number:
Newport Hobby House Limited
146 Broadway
Newport, RI 02840-2748
(401) 847-1515
Here's a yahoo search page of RI hobby shops.
http://local.yahoo.com/RI/West+Warwick/7737272/Recreation+and+Sports/8120285/Hobby+Shops/