From my experience, I would recommend that you find fiberglass rods. They are much more rigid than acrylic. I used 1/2" fiberglass rod in my rock work and it's strong/rigid as steel. Unless you use pretty thick acrylic, they tend to bend and flex.
I got my fg rods from a local plastic place that carries acrylic as well. I found this place with a quick search.
http://www.tapplastics.com/shop/product.php?pid=159
Good luck.