I'm sorry for the diagnosis. I lost my kitty to renal disease earlier this year.
Are you sure you can get cypro without a prescription online? There are places that sell it, but normally they require an rx from the vet. Your vet should be willing to write you a prescription that you can fill anywhere you want.
Just so you know, cypro is an appetite stimulant, but depending on how advanced your kitty's CKD is, just an appetite stimulant is often not enough. Kitties with kidney disease almost always suffer from nausea and excess stomach acid and need to have them treated before an appetite stimulant is effective. Otherwise, your kitty is hungry, but still nauseated and unwilling to eat.
Again, it would depend on your kitty's numbers, but Cerenia or Zofran to control nausea or vomiting, and an antacid like famotidine (Pepcid A/C) or ranitidine (Zantac) can do a lot to get a kitty eating again.
Also try turning wet food into a soup by mixing it with a lot of water. Many CKD kitties prefer to lick food.