I also got mine at Discount Tire but what they had to do was ship one from another state...took a few days & I had my tire. Quantities are limited, but the discontinuance is fairly recent (recent, being a relative term) so production stock is still fairly available, but dwindling. The tire stores that tried to order form the manufacturer on my behalf were unsuccessful due to production stopping. Not real sure how Discount Tire is able to have such a surplus, but out of 12 tire places I called, I was only able to locate one from Discount Tires (And Les Schwab). Still have the list of dealers I called...being told "no" time after time.
NOTE:
Les Schwab did order the tire for me (they are affiliated with Discount Tire), but refused to sell it to me at the time I tried to pick it up...because they wanted to know what kind of "car" the tire was going on. When I told them it would be going on a Toyota MR2 (Same rim dimensions as the Spyder), they told me to bring in the wheel/rim and/or the car in order to prove it was going on the car. They would not give me the tire in the end, even though I had pre=paid for it at the time of order. Instead, they refunded my money. I am not sure why they would care what I do with the tire (hell, I could be using it for a tire swing in my front yard) after purchase, but they anoint themselves "Tire Police" and refuse to sell it to a consumer if they "Think" the tire is not going on a vehicle they approve of. Personally, I think they overstep their bounds, as they would hold no liability once the tire is sold.
My local list of places called but couldn't get the Kumho 225/50/15 due to discontinued production:
i have had wrong tires that customers wanted installed, i would still sell the tire & would not mount & balance or at the very
least write on invoice that tire/rim IS NOT TO BE INSTALLED OR USED on any car. With very rare exception i would still sell customer the tire. As you stated if you wanted to make a swing out of it, have fun.