You can always decimate the samples of the ADC with any microcontroller. Therefore, any ADC with at least twice the maximum sampling rate of your needs will be appropriate. For example, the ADC141S626CIMM/NOPB from TI might be an option.
There is a series of precision ADCs, albeit on higher resolution side, from Analog Devices. It is AD77XX which are 24-bit serial ADCs with in-built programmable digital filter and serial interface and dual channel inputs. The sampling rate is also low, a few kHz and are specifically targeted for Stain-gauge and loadcell applications. Give a look and you should find it much suited for your job.