Answer: Monrovia is a wholesale only company and does not sell through a catalog, however you should be able to locate garden centers near you that carry their products (and others) using the zip code search at the Monrovia web site. Most full service garden centers and nurseries will stock berry plants in the early spring, sometimes in containers and sometimes bare root. You could check with the stores near you to see if and when they expect to have them and what varieties they usually carry.
Alternatively many mail order nurseries sell blackberry plants. You would want to order now for shipment this spring. Here are two reputable nurseries to get you started.
and Edible Landscaping
Please note you may need to cut and paste each url in full into your browser to make it work correctly.
Q&A Library Searching Tips