Can I buy tourist day pass at any MTR station?

You can obtain these kinds of card in the following places:
1. MTR Customer Service Centres: All stations (except Racecourse station)
2. Light Rail Customer Service Centres: Ferry Pier Terminus, Leung King, Town Centre, Yuen Long Terminus, Tin Yat, Siu Hong and Tin Shui Wai stations
3. KMB Customer Service Centre: Sha Tin Central Bus Terminus
4. New World First Ferry Octopus Card Service Centres: Piers of Cheung Chau, Mui Wo, Peng Chau, Central Piers 5 & 6
5. New World First Bus Customer Service Centre: Admiralty (East) Bus Terminus

So you cannot buy the tickets at a hotel. MTR Stations are good places for you to buy. :-)