http://www.usplastic.com/catalog/item.aspx?itemid=37217&catid=610
This page describes 2-way and 3-way joiners. They come in 8 foot lengths but we could cut 4 inch segments from them. The description says that it holds “butt ends together”, I’m not trying to be funny, I think we need to get the right terminology to find the solution which is probably already out there.
As for display experts, my brother used to create displays for a museum in Harrisburg and he is now an architect. I just emailed him. But you are right, it was a children’s museum with interactive exhibits and they tried to build most things to be indestructible, but he would know what company or catalog to check out.