Thanks to J.OT13 for pointing me to this thread; a few tools that I came across that may be of interest:
Smappen: You can use this to plot the population that lives within X travel time of a location (this is a paid tool but I was able to use the free demo multiple times by using it in a new private browsing window)
TravelTime is another one I found but it doesn't show population in the catchment area.
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