Com o bash, você pode fazer isso:
# the set-up
touch 20029181109173105_MAN_TDR.PLU 20029181109185001_MAN_TDR.PLU 20029181109185301_MAN_TDR.PLU 20029181109185601_MAN_TDR.PLU 20029181109185901_MAN_TDR.PLU
current=181109180000 # this would be 'current=$(date "+%y%m%d%H%M%S")'
# the pay-off
for f in *PLU; do
if [[ $f =~ ^.....([0-9]{12}) ]] && [[ ${BASH_REMATCH[1]} -gt "$current" ]]; then
echo "$f"
fi
done
20029181109185001_MAN_TDR.PLU
20029181109185301_MAN_TDR.PLU
20029181109185601_MAN_TDR.PLU
20029181109185901_MAN_TDR.PLU