I would like to create a matrix on an existing item. Is that possible? I don't want to recreate the item because then I'm going to lose the purchase history on the items. Is there a work around this?

Not using core functionality. Once an item is created you can't change the type You can make the child items and assign this as a parent using a custom field or the native parent field. But the matrix funcationality wouldn't work

Agree with above