HI.
1. When you mention, that you seek to demonstrate non-inferiority, I automatically think about non-inferiority clinical trials, that show that the new treatment is not inferior to current standard of care. If this is what you seek to do, than this guidance may be of some help. https://www.fda.gov/downloads/Drugs/Guidances/UCM202140.pdf
2. On the other hand as I understand you want to compare 2 proportions, this could be done manually (something like this http://udel.edu/~mcdonald/statfishers.html) without having raw data, and after that you can estimate power (https://support.sas.com/documentation/cdl/en/statug/63033/HTML/default/viewer.htm#statug_power_sect0...). In SAS University edition: tasks and utilities>Power and sample size>test of proportions.
3. From regulatory perspective it is wise to seek scientific advice, because if you want to establish non-inferiority, you need to very clearly define the non-inferiority margin and robust rules in doing that are lacking.
4. Trying to establish that population B is non-inferior to population A could result in methodological issues.
If you would clarify the problem, I could perhaps be of more help.