If you are looking to get some without doing any modifications you will be limited to the clamp on kind , which are not worth spending $ on .
I disagree. While there are some clamp ons that aren't worth 2 squirts of owl poop, the DownEast rod holders are great. I have both the single clamp(D-10) and double clamp(s-10) models, and they are both built very stout. If you do not want to drill holes, or are worried about how to mount the driftmasters or other brands, the downeast holders are the way to go.
Down-East Sportscraft's "Clamp-On" Rod Holders