Buying bitcoin from a specific block?

I want to buy 5-10 million sats that were mined in block 395,731. No particular reason other than it was the block that was mined just 2 minutes after my son was born. I figure it might be cool to give him when he gets older. How possible and how stupid is this idea, and why does it seem to be so hard to follow these 2.5 billion satoshis and figure out who has some to sell?