Solutions for Hollow Cheeks?

This question has been well addressed and any filler (commercially available or autologous grafts) can essentially be used.:

Radiesse
Juvederm Ultra or Ultra Plus
Restylane or Perlane
Sculptra
Autologous fat injections or dermal-fat grafts
Implants (silicone, polyethylene, PTFE, polypropylene, hydroxyapatite, etc)

Depending on the volume required, some may be prohibitively expensive for the volumes required and for maintenance.
Also take into account your personal health and fluctuations in weight which may have an effect on the long term results.

it is very important to preserve (or restore) soft tissue volume in the lower lid. When I review with eyelid surgery patients some photographs from their twenties, in most cases we find that years ago there was no visible demarcation between lid and cheek, but instead a smooth, gently convex curve extending downward from the lower lid margin.

In patients who have developed deep 'tear troughs' at the junction of the lower lid and cheek, adjacent to the side of the nose, the meticulous grafting of fat harvested from the patient's abdomen, hips or thighs can build this area back up and nicely restore a more youthful contour. In some blepharoplasty patients this depression or 'hollow' extends horizontally across the entire junction of the lower lid and cheek, and this must be corrected to obtain the ideal postoperative result.

In select patients, lower lid rejuvenation may consist of conservative reduction (not removal) of the lower lid fat pads or 'bags', in combination with structural fat grafting of the 'tear trough' hollow immediately below. As with all aesthetic surgical procedures, it is absolutely essential to customize the surgical plan to the specific needs of every patient.