There are a few places online that do this. One of them is https://etherscan.io/gastracker. Another is https://ethgasstation.info/. If you do a Google search for “ethereum gas price tracker,” you should be able to find one pretty quickly that you like.
Typically, they break prices down into three recommendations that correspond to a low, medium, and high chance of going through for a given block. I’ve found that there are times when the network is so busy that it still takes hours for a transaction to go through, even when the gas price for my transaction is set very high. Most of the time, though, things are relatively stable, and you should be able to work with the numbers you get from these providers.
Many of them have API access as well. They tend to want to know who you are (by way of a token) for API services, and sometimes to charge you money. Some will let you hit their API for free, but throttle heavily.