you should just make some extra KH buffer solution to bring up the KH.
component 2+ = sodium bicarbonate + component C strong. as long as you add component c strong to the solution, i dont see any issue.
here's the math if you havent done it.
1G BRS sodium bicarbonate = 6.4G of solution, 50ml = 1.3 dkh for 27g of water, $20 = $3.13/G
1.2kg AF KH buffer = 3.94G of solution, 50 ml = 1.3 dhk for 27g of water, $12 =$3.04/G.
please tell me why you want to use anything else other than AF KH Buffer?(Beside if you have ton of sodium bicarbonate already)