Loaner (noun)

1. A person or thing that is lent, especially temporarily.
2. An item that is lent to replace another item that is being repaired or serviced.

Origin:

From the verb "loan" meaning to lend.

Examples:

1. The loaner car was provided while hers was being repaired.
2. The loaner equipment was provided for the duration of the repairs.
3. The loaner tool was borrowed from the hardware store.
4. The loaner item was returned when the original was fixed.
5. The loaner bike was used while the other one was in the shop.