Yes you can modify the Harris to fit a pic or Arca rail.
I think the Harris is a good place to start, fairly cheap and does the job.
It used to be if you wanted a cheap bipod you buy a Harris, then upgraded to an Atlas bipod if you were a real operator.
But now with so many good (expensive) options that all do things slightly differently you really ought to know what you want out of a bipod before dropping some serious money on a flash bipod.