2009 Prius Spare Tire & Tire Sensor Question

Hi All,
Thanks for all the great support you all offer here. Having this forum to post and learn is really invaluable for someone who is not a huge car person.

I have a 2009 Prius and long story, but the spare tire got pierced while in the compartment so I am in the hunt for a new one. The OEM spare is T125/70 D16. There is nothing wrong with my wheel. It seems expensive to just order a new tire and have a tire store put the tire on the wheel. There is someone selling a spare tire never used from a 2009 Elantra that is T125/80 D15 for $25. Does anyone know if this will work on an 09 prius? I searched but haven't found anything conclusive and getting confused about it all. Any thoughts?

Also, one my tire sensors is malfunctioning causing the light to blink repeatedly, and then ultimately stay on. It's not the pressure in the tires, they are all at exactly the same amount. Discount tire wants $65 to fix the sensor that is broken when they change my tires. Tires are at 4/32 so need to be replaced anyways. Is there a cheaper resolution to the tire sensor fix that anyone has found?

Thanks as always for your help.