Hi S – Unfortunately apart from Benzoyl Peroxide, the rest of the topical creams require a prescription in Singapore.
The National Skin Centre pharmacy is your best bet (and probably cheapest option) for all the creams above, including Epiduo, Retinoic cream and Clindamycin.
Otherwise, private dermatologists/aesthetic doctors and GPs with a special interest in skin will likely stock some or all the above creams, in that order of likelihood.
Cheers