Interesting! I can remember when I was in high school and taking sewing classes, I used to go to a factory outlet to buy double kits. I used to make pants suits with them! (Remember pants suits ...and leisure suits for men! haha!) I still remember making one of my high school girl friends a pair of pants and a cute boxy little jacket for her birthday and it looked so cute on her!
I also remember a really pretty pink plaid jacket with dolman sleeves that I made myself out of bonded wool. Remember bonded wool? Do they even make that anymore? It was so easy to work with!
If I should come across any double knit, I'll let you know. I go to thrift shops alot and always look through the fabrics. You never know what you might find!