There are two ways that can be used. If you still have some of your own hair in this region use that, then integrate it into the wig. I have done this succesfully with my existing remaining temple hairs, sideburns and nape hairs.
The other way is, as you suggest, get it custom made. I asked Eric at NWL to use lesser density in this area and vent the hairs back, using 2 inch thin Swiss lace front which extended to the temples. The Swiss front was also blond hair, the rest of the wig French lace with 1B. I then dye the blond hair to match the rest, thereby ovvercoming the visible hairline knot issue.
Unfortunately, full caps are still unavailable at NWL.