you may be able to get profender online but *legally* your vet would need to do a prescription for it for you to get it as it is a POM-V product.

its probably best to get it from your vets.

BUT.......

i would check the prices online and then take them to your vet and ask if they can match it. sometimes practices cant even buy the products for the price the online guys are selling for so they may not be able to match it, but they may well drop their price, especially if you have lots of cats so will be buying a lot!

Good luck