While visiting your dermatologist look around the waiting room. Most often you can find displays of free sunscreens, lotions, information and I found laundry soap!
I took home one wash load of All with stain lifter free and clear. Sample says #1 Brand recommended by Dermatologists Allergists & Pediatricians for sensitive skin
If you think one wash load would not be enough for a trail just ask if you may take two.