It may be true that in our modern world, where time is short, a set of stones is a relatively expensive prospect. But, if I had a day to spend on the beach, or on the side of a large river, I am fairly confident I could gather a set of stones before the sun went down. One set light gray and the other darker. In truth, they don’t have to be nearly as perfect as the clam and slate producers would have you believe. The game still works with significantly under-sized or even grossly over-sized stones.
To wit: Playing Go IRL pictures - #419 by Plum_Talk
For a ‘board’, simply drawing in the mud or sand with a sharp stick would do the trick, but hurry up because I’m tired of looking for rocks and want to sit down and play already!