Hi,
you both can search for your problem in google with the keywords like stair parts, stair treads. You eill definately find some good sites, I've found a good blog related to the same ie. stairsupplies.com/blog. It may be helful for you. Good luck!
I am partially understanding your requirement. However if you could elaborate it a little and post some pic may be we would be in a better position to suggest. As per my understanding you are looking for the strong railings. I guess you may find a lot of beautiful and modern option if you search...
Well you need to take proper guide and services of professional for installing railing on interior stairs. For guide you can get a book from library or can read online blogs or article on stair & railing just like Stairsupplies Blog