Boater's World or West Marine have what you're looking for and will work fine. On my walk-around I mounted Perko rod holders (about $29.95 each) on the bow rail, but on the uprights that support the horizon section. You can put one on each upright on each side to maximize your ability to have rod holders.
Just remember when you are traveling, having rod holder where you want to mount them, the rods will need to be held in place with bungees. Your idea will work great for flounder and other types of bottom fishing.
I use mine all the time like that. In fact, the rear-most holders on the bow rail I use for trolling for stripers in the fall.
Having a three or four rod holder mounted on the cabin in the walkway area is cumbersome when trying to get forward for anchor chores etc., when in choppy weather. I thought about that also and opted for the above.
Good luck.[excited]