Downloading firmware for the Huawei U8500 (also known as the MTS Evo or Beeline E300) can be difficult because the device is very old. The most reliable resources are community forums where enthusiasts still archive files.
Since many original download links (like RapidShare or old file hosters) may be dead, look for "Mirrors" or recent posts within the forum threads mentioned above. Huawei U8500 - Прошивка - 4PDA skachat proshivku dlia huawei u8500
Ported MIUI builds for Android 2.3 Huawei U8500 - Прошивка MIUI (OS 2.3) . Installation Tips: Downloading firmware for the Huawei U8500 (also known
Community-built versions based on official software Huawei u8500 - Модифицированные прошивки . skachat proshivku dlia huawei u8500