As shown, I don’t have the middle piece that’s missing.
147x77
Check out this KALLAX from IKEA.
Here’s a little more information:
https://ingka.page.link/WJpQurDyk4ZiGRWL9
Ikea Kallax 4x2 (Wythenshawe M22)
This offer has been gifted to someone and is no longer available.