So with that in mind, I went looking for resources to make your own doll clothes.
Julia Printable Steampunk Doll Clothes via Etsy
These are probably the most interesting, and maybe least work-intensive ones I found. For $2.99, you get a downloadable template that can be used to make doll clothes for both small and large dolls. The doll clothes are made entirely from paper, and held together with tape. How durable they are probably depends on the weight of the paper you use, as well as how careful your child is while playing. There are free samples on the artist's website, if you'd like to just try them out.
Airship Amelia Steampunk Soft Doll Printed DIY via Etsy
This one is pretty cool. You have to sew her yourself, but the kit comes with all the pieces printed on fabric (printing done by Spoonflower, so it should look quite good), no coloring or embroidery needed. The doll stands at 8 inches tall, and I think it's pretty awesome.
Simplicity 1392 Steampunk Doll clothes for 18" Doll
Believe it or not, Simplicity has a steampunk pattern pack for 18" dolls. Now these are intended to fit American Girl dolls, but my experience is that they should also fit most other 18" dolls, like the Our Generation dolls sold at Target. Some will fit Disney's toddler princess dolls, depending on which doll you have; my daughter has the Merida one, which has a little bit of a belly, affecting the fit. This option is the most involved, since you have to buy fabrics and notions, measure, cut, sew things, notion them, and so on.