Download Android ICS 4.0.3 Stock Firmware for Lenovo IdeaTab A2107A tablet from here or here. Download another Lenovo firmware from here.
Archive name: A2107A-H_S314_120723
Archive file size: 399 MB
Model: Lenovo IdeaTab A2107A tablet
Platform: MediaTek MT6575
Build number: a2_3g_data-user 4.0.3 IML74K eng.buildslave.1343033523 release-keys
Caution: Please do not update firmware unless you know what you are doing, you really want it or it is absolutely necessary. Firmware updates may occasionally have bad results, like bricking your device, temporarily or permanently. The firmware update process is done entirely at your own risk. Before attempting to update the firmware, back up your data.