You might check but I'm guessing the 3rd gen Prius spare (doughnut) is the same as the Gen. 4, if it is, get thee to a junk yard, one out of a wreck should be a lot cheaper than a new one.
Yes: "theoretically" even the spare tire should be replaced at the 10 year mark. OTOH, they lead a sheltered life. Still, if you're buying salvaged, check the manufacture code on the tire, and look it over closely for cracking.
-------------------- Mendel- I am buying this car because of MPG- I want the highest I can get + the Eco is also the lowest price with the LiON battery which is my other requirement- Hence the Eco. I only want the spare when I am on cross county trip as a back -up. I do not change tires unless I do not have cell phone reception so I will only carry it then. And the deal is set- I just sent the signed contracts back to them today via FedEx - I told them we had a deal if they met my price-$24,820- they came down $964 off their 'Best Price' to meet me and I have shopped many dealerships and this is a great price for this part of the country and that includes adding Body Side moldings and Trailer delivery 250 miles to my home this Friday. Once I make a deal I stick to it- my salesman told me he could get me a deal on a spare wheel- I can get the tire mounted somewhere near home. I am excited for the delivery Friday 1/5/2018... Thanx for all you assistance . . . ---------- I am buying this car because of MPG- I want the highest I can get + the Eco is also the lowest price with the LiON battery which is my other requirement- Hence the Eco. I only want the spare when I am on cross county trip as a back -up. I do not change tires unless I do not have cell phone reception so I will only carry it then. ---------------- Yeah I most likely will end up with a new on- I am a pretty good shopper- I will wait till I find the best deal. I may just but the wheel and get the tire purchased mounted near home. I will check Junk Yards- but I am finding that Prius are a bit thin on the ground so that may be a fruitless quest... -------------- Good suggestion- I will do that ...