There is no flock or similar command for Solaris. If I want to do simple locking I use mkdir as it's a atomic operation and avoids potential race conditions with the usual check file exists/touch combination.
if ! mkdir /tmp/lockfilelockdir &>>/dev/null
if [[ $? -ne "0" ]]2>&1
then
echo >&2 "Lock exists exiting"
exit 1
fi