Suggest you pick up Alex Anderson's hand quilting book. She shows both left and right handed quiting.
I am told the thimbles with opening in the top work well. The Roxanne thimbles have these but are pricy.
Unfortunatly most LQS don't have a large variety of thimbles to try. it is just trying them out. Sugest you get the less expensive ones to praceice and start with and then if they work go to a better quality neede. Most quilters will start with a #8 between and work down until they find the size that is comfortable for them. I use a #9 which fits my fingers better. Also try and find a left handed quilter to help you rather than try to rearrange the visual from a right hand quilter. Don't obsess with getting very small stitches at first. Size comes with practice. Learn to make them even with good penetration to the back of the quilt. Practice on 1/8" gingham check for consistency in size. It helps.