I think I just become a fan of Côte&Ciel bags, their bag design is unique and nice. If you want to get their bags in Singapore, you can check out Cumulus at Wheelock Place or their online store cumulus.sg.
Address: 501 Orchard Road, #02-14 Wheelock Place, Singapore 238880
Contact: +65 6733 3486
Cumulus also sell sleeves from Côte&Ciel at their sister’s store, Nimbus, which is also located on the same floor at Wheelock Place.
501 Orchard Road, #02-10 Wheelock Place, Singapore 238880
Contact: +65 6733 3286
Alternatively, if Cumulus do not carry the design you wanted and if you can wait, it is better to get it from Côte&Ciel site itself as it is cheaper.
For my Spree Messenger Bag (Grey Melange) (Medium), they are selling for €110.92 (S$185) and shipping to Singapore is another €25.17 (S$42), which brings a total cost of about €136.09 (S$228).
The same bag that is listed on Cumulus is selling for S$260 which is slightly more expensive.