Most biological buffers (examples: Tris, HEPES, phosphate) are usable in this wavelength range. If there is a small absorbance, it can be subtracted. What pHs do you need?
The Good's buffers, Tris, and imidazole cover the range from pH 5.5 to 10. Phosphate buffer can also be used from about 6-8. Some of these organic buffers may have UV absorbance.