Lightools Research, my employer, as several products that can and have been used for the application you described, the visualizing green (GFP) mice. The LT-9500 Illumatool Tunable Lighting System is the model most researcher use for viewing. For example, in a recent paper1, Yang, et al used the Illumatool for real-time imaging of GFP-expressing tumors growing and metastasizing in live mice, affording "unprecedented continuous visual monitoring of malignant growth and spread within intact animals". The Lightools Illumatool systems have positive results with both GFP and RFP.
1. M. Yang, et al., "Whole-body optical imaging of green fluorescent protein-expressing
tumors and metastases," Proc. Nat. Acad. Sci., 97:1206-1211, 2000.
John S. Fox
ltr at lightools.com