You can pick an exchange and look at trade history.

For example this link takes you to the trading page on Coinbase

https://www.coinbase.com/en-ca/advanced-trade/spot/BTC-USD

On the side there is a column called trade history and you can see all of the bitcoin trades as they happen. Since this is the price people really are exchanging fiat for bitcoin at then you can know this is the price of bitcoin at the current moment (at least the price on Coinbase, as I said in a previous message there can be slight differences between exchanges)