The Census Bureau provides county level estimates of population and housing units here:
https://www.census.gov/programs-surveys/popest/data/data-sets.html
I'm wondering if these estimates are available at a PUMA level as well? If not, how would one go about "cross-walking" county level estimates to the PUMAs?
PUMAs should be available for 1-year ACS data products. You may need to expand the filters to include non-standard geographies. PUMA is summary level 795 if you can search that way.
The PUMAs are available in the 5 year and 1 year ACS. However, where do you get the exact count of the total number of people/households in a given PUMA? Isn't the ACS only sampling a certain number of households/people from everywhere?