You can not find it because there is none.
ICAO does not prescribe a minimum ROD. Nevertheless they do expect that you minimize your ROD/ROC to max 1000'/min the last 1000' to avoid TCAS TA's or even RA's.
If you want to know what the minimum descend rate in an terminal area is you should look in the AIP of the respective country if there is something writen about it. Just like in the UK AIP about London ACC.
In a descent I will always fly a minimum of 500'/min to keep a descent arrow on other aircraft's TCAS display. This I practice as well in a holding since there will be traffic 1000' below me.
So everybody who claims 1000' is the minimum ROD is wrong, unless it is written in the respective AIP.