Lots of nurseries have rhubarb for sale. We use Johnny's Selected Seeds (in Maine) and have had wonderful luck with their plants/seeds.
HOWEVER you should check with your local extension office or do some research, because rhubarb does not do well in hot climates. I have access to rhubarb - my mom has a huge patch. Last fall someone from Florida asked if I would send her some, but when she checked, she found that it would not survive the hot summers and warm winters.
So you should try to find nurseries that carry plants designed for your climate, as opposed to ones that do well in other locations... but you probably know that already.
If you decide you want to try rhubarb, send me a PM, and I would be happy to dig a root or two for you - but the time for that would be in the fall. Spring is when the plant is trying to grow, then late summer is when it's putting in energy stores for the following growing season, neither of which you want to interrupt... so around October is the time to dig it here.
So, check out the chances of success in your area, and let me know if you want to try it.