[BirdDog]

You can order the fluid from Amazon for $67.07 for 5 liters with free shipping.

https://www.amazon.com/Pentosin-Long-Life-Fully-Synthetic-1058206/dp/B00JMAQ0LW/ref=sr_1_2?ie=UTF8&qid=1532365820&sr=8-2&keywords=Pentosin+ATF-1&dpID=41wz6afAyIL&preST=_SX300_QL70_&dpSrc=srch

That's enough for one fill and drain. SO, to fill and drain 3 times, order 3 of them.

That's about the cheapest you are going to find it. O'Reilly's also sells it, but my guess is that they will only have 1 liter bottles in the store, but you can order the 5L size and have them delivered to the store. It's $76.99 for 5L.

https://www.oreillyauto.com/detail/b/pentosin-4623/chemicals---fluids-16461/maintenance-chemicals-16867/power-steering-16618/power-steering-fluid---vehicle-specific-13543/c378387a8aa0/pentosin-5-liter-transmission-fluid/1058206/4650324/2003/pontiac/aztek?q=Pentosin&pos=12

Hope this helps!