I don't think that any of us can beat your travel trailer sewing room. That sounds great.
Garage sales, church rummage sales, and thrift stores are where I have obtained most of my large stash of fabric. When word got out that I make quilts, friends started bringing me sacks and boxes of their scraps. One young woman must have given me her whole stash. While helping her pack up her stuff to move to her new husband's home, the woman's mother saw a stack of fabric that the younger woman had bought for crafts that were never even begun. The mother said, " Either take that stuff with you, or give it away. You are not leaving it here!" Well, she elected to give it away, and I was the lucky recipient.
My husband's not so sure about the "lucky" part. He took a look at the stacks of boxes of fabric in my sewing room and said, "Enough already." Now I only go to the garage sales within walking distance, That way, I get my daily exercise and can only buy what I can carry home.