I need a word for: an item that can be substituted for another due to that item not being readily available...OR
what is the word for something that is used as a substitute while in a bind?
The word you can use is: Substitute
Substitute (n) : a person or thing that takes the place or function of another
Link for the same: Meaning of substitute in Merriam Webster
Off the top of my head, I'd say "replacement"; however, I'm now intrigued by the word "bined" at the end of the query. I wonder if the asker meant "in a bind". https://www.wordreference.com/es/translation.asp?tranword=in%20a%20bind
Some synonyms for "substitute" that also express it is not the genuine item:
Surrogate (often used for persons)