You need to contact LOCAL TRAVEL AGENCIES. IF there is a special rate or promotion available, THEY are the ones to get them.
Interestingly, some banks also get wind of special rates available now and then. If you have an insider contact at your bank, ask them too.
Most AI's are not setup to handle local call-ins. They sell rooms en bloc bulk to wholesale and tour operators.
We once tried to deal with IberoStar for a very special arrangement for almost $15'000.oo... they could NOT handle it and referred us to tour operators and to come back to them for special arrangements once we had a reservation!
Others like RIU have their own web site.... however, one will mostly find better offers for their hotels elsewhere online.