Does the spell specify that the material component need be the same as the one used in the attack?
As part of recent errata to the green-flame blade and booming blade cantrips, their material components have been amended to "a melee weapon worth at least 1 sp" (Sword Coast Adventurer's Guide, 142).
If the attacking weapon and material component do not have to be the same, then can you use a separate weapon for the component?