You can get shRNA as packaged lentiviral particles from Sigma, Santa Cruz, and many others - just put them on your cells and do analysis a few days after transduction. If your cell line tolerates transfection well, just get the shRNA plasmids and transfect them in as that is much more cost-effective. You may want to try using a comparison-shopping webisite like Biocompare, or ask a group that has successfully knocked down your gene of interest to see what method they used. Good luck!

I have good and bad experiences with Sigma Mission shRNA products (http://www.sigmaaldrich.com/life-science/functional-genomics-and-rnai/shrna/shrna-search-and-order.html), they are quite simple to use, for example you can buy either the plasmids, the already transformed bacteria in a glycerol stock or the lentiviral particles (probably what you want). You can also buy them as a pack of five plasmids with different sh targeting sequences. However, although I found one protein very easy to knockout using this system, a second different protein proved very difficult.

We used products from Openbiosystems with good success.