I found the iPod Touch 4th Generation LCD connector replacement part (requires soldering skills) for the logic board at Global Direct Parts. However, they are wholesale only and do not sell to individuals.
The replacement for the digitizer connector is also available from Global Direct Parts. The digitizer connector is on the opposite side of the logic board from the LCD connector.
This is not a job for the inexperienced, nor the faint of heart. If you do decide to tackle this replacement and your mind eventually boggles at reassembly, contact an iPod repair expert - but keep in mind, they usually do not do soldering. There are several on the Internet and the average charge is $25 for the initial evaluation. THEN they will give you a quote on the repair.
I have repaired previous iPods, but found the iPod Touch 4th Generation to be very problematic. My rating for the novice would be 1 out of 10 on repair difficulty (10 being the easiest.) Unless you are already an expert, my advice would be to send the iPod Touch 4th Generation to an iPod repair expert in the first place, rather than attempt Digitizer/LCD* replacement on your own.
Hope this helps.
*Keep in mind the OEM Digitizer/LCD is ONE factory assembled part. Best not to be tempted to purchase individual LCD or Digitizer parts. In addition, the iPod experts will not accept replacement parts you send with your iPod.