Don't make it. Just don't. The exact color scheme you're dreaming of in a fabric? It doesn't exist. And even if it does, it will require you to buy 4,323 other bits of fabric, oddments, accessories, and pom-poms to get the look you're going for. And once you get home with the largish bag of items to make the 4-inch-square doodad you're imagining? You will realize that you just spent $77 for something that was going to cost you $30 (plus shipping).
Let's not even start on the amount of work you need to do to transform the pile of scraps that is sitting on your worktable into something serviceable. Remember, there are fourteen other projects hiding under the worktable that also need your attention. Projects that were only going to take "a minute". A minute = 2 months, give or take a week. Projects take time. And energy. Things that you have in short supply right now.
Self, I'm not kidding. Don't make the thing. Be happy with the approximation you found at the store. Know that you'll be able to use it immediately upon opening! That you won't be waiting to wear it in the spring (when it was supposed to be for the winter) or that Alice will be able to enjoy it thoroughly while she still can. At the rate you're going, she's going to be driving a car by the time you're finished.
I know you have mad skills, self. You do! And most times your little creations come out looking fantastic. But seriously, you need to make room for the 1 in 3 times when the end result is a little... less than savory. Because it really does happen: the thing you've been thinking about in that noggin of yours materializes as... something else. Something that you'll never be happy with. Something that looks goofy. Something that doesn't work all that well. I know you think you can fix it. I know you think that just one more trip to the fabric store is the answer. But you know as well as I do that once is never enough. That the second trip leads to the third which leads to the fourth and before you know it you're working on the World's Most Expensive Flimflam. And it's six months later and the one you could have bought in the first place is on sale. For half off. With free shipping.
Just go buy it instead and we'll all be happier.