If the shape or size of your head makes it difficult to find a proper fitting wig, you may want to consider having one custom made. This involves having persice measurements taken of your head, then a wig maker will construct the wig cap that will be a perfect fit!
This can be done for all types of wigs, both synthetic and human hair. Surprisingly this service is quite reasonable, especially if you are investing in a high quality wig.
You also can have a pre-made wig professionally sized.
If you've had a hard time finding a good fit, going custom could be a great option for you.