xlsb can be read by newer versions of Microsoft Office Excel, OpenOffice Calc, or LibreOffice Calc.
So all you have to do now is open the file in one of those programmes and export it to xlsx.
CSV -> xlsx
This can be done easily with pandas, a python package.
import pandas as pd
df = pd.read_csv("/path/to/file.csv")
df.to_excel("/path/to/result.xlsx")
xlsb -> xlsx
Pandas 1.0.0 added the support for binary excel files.
import pandas as pd
df = pd.read_excel("/path/to/file.xlsb", engine="pyxlsb")
df.to_excel("/path/to/result.xlsx")
In order to use it you must upgrade pandas, and install pyxlsb and 'openpyxl':
pip install pandas --upgrade
pip install pyxlsb