@Chris & China (GA) alerted folks to the problems that Marks Marine Pharmacy was having with getting the full shipments they had requested. They are offering the Basaglar insulin as an alternative. Basaglar is a bio-similar insulin, so you will probably see the same general results with Basaglar as you do with Lantus.
More info in this thread
http://www.felinediabetes.com/FDMB/threads/canadian-pharmacy.228336/#post-2557058
Prozinc is another option for your cat. This is one of the in-and-out insulins, usually lasting 10-12 hours in a cat, sometimes up to 14 hours. Some cats do well on Prozinc.
If you are thinking about Prozinc, you might want to go over to the Prozinc ISG (Insulin Support Group) and read through the "Sticky" or pinned posts at the top of the forum.
Prozinc / PZI forum