Use of alternate component in BoM

In our business we can use alternate items during manufacturing process. For example, a 5 lbs bag of salt (primary) vs a 10 lbs bag of salt (alternate). Our main component 5 lbs bag may or may not be available at the time of material consumption. I am wondering if there's a good way to handle this situation.

I thought about usng 10 lbs bag as a substitution item. However, I am not sure if this will give folks the ability of choose between the two.

Any input is highly appreciated.