Add ID information from one dataframe to every row in another dataframe without a common key
Well, it turned out I accidentally answered my own question in the title.  My answer to this is to insert a new common key into both dataframes, then delete the new key after the 2 are merged.  Maybe there is a more elegant way, but this works.

df.insert(0,'mykey','abcdef')
df2.insert(0,'mykey','abcdef')
df2=pd.merge(df,df2,how='outer',on='mykey')
df2.drop(columns=['mykey'])


Where mykey is the new common key, but make sure it will not match any existing columns, while 'abcdef' is random, but needs to be the same added to df1 and df2.