Looking closely (I think I am looking at the same quilt) that bright yellow fabric seems to be a tone on tone stripe. This fabric might be a close match, just not striped:
https://www.equilter.com/product/293...k-lemon-yellow
Just by the bye, yellows are often hard to find. There are always lots of blues and greens in fabric collections, but not a lot of "just yellow". I always check the yellow section in any quilt store I am in, looking for good yellows to add to the stash.
I love what Bonnie does, but in this quilt I do not like the yellow as sashing! I think it overpowers the blocks, which tend toward the dark. I'd audition some purples and dark reds for that quilt.