Seeking for illustrator to revamp the graphics for my book

Hello everyone. I am looking for an illustrator to revamp the illustrations for my book. The picture below is the book cover created by the previous illustrator.
I loved It very much but the problem was the inside illustrations. We're disappointed with the results. The illustrations were amateurish, the characters looked mangled, and it's clear that the project was rushed.
We are quite flexible with our timeline and budget but we want to get back our money's worth. Unfortunately, this experience with the previous freelancer was very disappointing.
So here's what I'm looking for:
I'd like to keep the "Detective Kat" design as it looks like a great logo.
The main character, Kat, can be more detailed. I love the colors to the previous illustrations but the details can be improved. I also prefer clean, uniform, and slightly bold outlines for the sketches.
Think of drawing using a ballpoint black marker.
Our target audience is children from 7-12 years old. We're aiming for books like Carmen Sandiego.
We have 14 illustrations to be redone for book 1, if we love your output, we have 3 more books being edited at the moment.
How to apply:
Please send me a proposal with your project bid (rate/full page illustration), your turn around time, and a link to your portfolio.
Our project rate is $35/illustration to start with. You can bid higher as long as you can prove your worth the investment. But, since I've been burned with hiring the wrong people, I'd more likely choose someone with a reasonable price not higher than $35 for this first book.
I'd rather start with paying a little low and give bonuses instead of paying high rates upfront.
Attached is the awesome cover and a separate word file for the inside illustrations that we wanted to be revised.
Send me an email at janine.pangantihon@yahoo.com