Since you are looking for cyclamate-based Sugar Twin, I presume you
mean the Canadian version of this sweetener. Unlike the
saccharine-based version sold in the USA, it's really hard to find.
But I managed to locate an online source for Canadian Sugar Twin:
Golbal Drugs is a Canadian online pharmacy, and they are shipping
non-presciption products to the USA, too. They offer Sugar Twin
(Cyclamate) Original Packets in several quantity variants (50, 100 and
200) for US$ 1.85, US$ 2.92, and US$ 4.80, respectively:
As Sugar Twin is not subject to prescription, you should not
experience problems ordering it from Canada via Global Drugs.
#115, 233-16 Avenue NW
Canada T2M 0H5
Website with online-shop: http://www.globaldrugs.com/pharmacy/
Search terms used:
"sugar twin" cyclamate:
"canadian sugar twin":
Hope this helps!