After last weeks post we return to an element of being an adult little gurl which is your interests and for me it's always been scouting and one difficulty in assembling a uniform is that quite simply unless you are looking at replica uniforms as worn from the 1950's to the 1990's and the Jeff Banks inspired uniform reboot coming in simply you won't fit in the official one today.
This you really need to reimagine a modern take one what a Brownie Uniform can be using tried and tested uniform colours.
The current uniform is very Hoodie Sweatshirt heavy, brown with yellow branding but you can take a leaf from current co-ed cubs and have a green jersey/sweatshirt you can badge up, very up to you if you want to attempt a brownie logo on the bottom like the Cubs one does.
Traditionally with the modern brownie uniform you have a sash you apply your badges to but you might as well take a leap out the co-ed cubs and place them on the Jumper
A bigger problem is the yellow polo shirt in brownies only goes up to 36 inch and is short in body with the Brownie Branding arranged in a semi circle on it but I use a regular schoolwear polo shirt that you can get in adult sizing that fulfils the function.That teamed with the brown skirt does make for a suitable uniform, modern but using traditional colours and easy to put together, sufficiently feminine for gurls like us.
That look isn't far remove from the early 1990's yellow top and brown cullottes option as shown in the 1991 Brownies Handbook that I have just we're introducing a brown skirt instead.
You could change the colours to blue for a similar take on Guides.