I really have no idea about ordering them from overseas & clearing Singapore customs, especially scopes which are meant for firearm use, for all I know you may need to clarify in person when it arrives that its for photography use. Also the scopes for firearm use cant be mounted to the hot shoe without an adapter.
Just drop in Orient Photo & check them out, they have an open frame design & a tubular design with hot shoe mount. IIRC they are made in the PRC, quite affordable.
Bushnell brand has scopes with hotshoe mount for photography. Amazon ships free to SG if orders are above a certain amount. For certain categories if the total exceeds S$400, GST will be invoiced. Same for B&H. If you find shipping charges to be high, use Comgateway (in Portand Oregon). Usually free shipment within US to Comgateway which in turn will ship to your home address for a reasonable fee and within a week or so by DHL. I've used that mode many times. DHL will include the GST if above S$400 total. I haven't owned a scope but I know of SG birders who use such.