I am not aware of a way to make the bubbles bigger, sorry.
For what it's worth, if you make the bubble plot smaller on the report page, the bubbles will be larger relative to the plot axes. I don't know if that helps at all but it might be more visually pleasing.
See how to use one filter for multiple data sources by mapping your data from SAS’ Alexandria McCall.
Find more tutorials on the SAS Users YouTube channel.