Three Chicago area retail hobby shops have been listed at the bottom of this page under "Traction Suppliers & Chicago Area Hobby Shops With Web Sites".
Each is unique and has carved out a particular niche in the O scale market besides stocking the normal modeling supplies found in other hobby shops.
Finding a retail store (hobby shop) which will stock trolley parts can be a problem. This is why trolley oriented vendors are listed at the bottom of this page. A hobby shop near your location can supply the items common to all model railroaders.
In posts in this blog are mentioned specific vendors for unique items covered in the post. When possible a link to the vendor is provided.
While I know there are other hobby shops which stock HO models, please recall this is an O scale oriented blog. I have very little knowledge about HO trolleys and models.
It's important for modelers to know the hobby shop(s) in his or her area to be able to obtain the day to day hobby supplies.
One exceptionally useful web page is the list of trolley specific vendors provided by the East Penn Trolley Club (EPTC). http://www.eastpenn.org/manuf.html
By the way, are you a member of the EPTC? Here is a link to the membership application. http://www.eastpenn.org/membershipapp2010.pdf Why not join?
The next biannual EPTC 21st National Model Trolley Meet is planned for May 2-5, 2013. It will be held at The Greater Philadelphia Expo Center at Oaks. Check out this link for more info. http://www.eastpenn.org/meet.html