Looking for 3 Light/DK acrylic yarn to pair up with Lion Brand Cupcake yarn

Hi, everyone! I have loads of Cupcake (now discontinued!) on hand and want to work on a brioche scarf using the multi-color Cupcake and a solid color yarn that matches the weight, density, etc. I tried a test swatch using Cupcake and some white Bernat Baby Sport. The Bernat was fluffier and slightly more dense than the Cupcake, so the feel and look of the brioche was uneven and wonky when comparing the two reversible sides. The only solid colors that Lion has on hand are not acrylic, but more "exotic" fibers that I feel wouldn't work either. I know it's a shot in the dark, but I'm hoping someone else will have solved the problem already and found a good pairing from another brand. Thanks for your help and happy knitting! :)