Hi,
Here are some links that may help you to replace the LCD module assembly.
The ifixit [[Topic:Lenovo Tab 4 8]] repair guide shows how to open the tablet so that access to the display assembly is possible.
Here is the Lenovo Tab 4 8 [https://download.lenovo.com/consumer/mobiles_pub/lenovo_tab4_8_hmm_en_v1.0_201706.pdf|hardware maintenance manual] which shows the same. It however also gives the part numbers for the various components in the tablet.
Scroll to p.36 Item #5 to find the FRU number (part number) for the LCM assembly.
If you search online using the ''part number only'' appropriate to your particular model variant, in the search term of your browser, you will get results for suppliers of the part.
Sometimes the part number is stamped on the back of the module somewhere if you wish to verify that you have the correct one but as there are only two choices, black or white I don’t think that it will be a problem ;-)