I can't find my usual diabetes tablet anywhere is there an alternative with the same composition as this Gliclazide 30mg Tablet MR?

It's frustrating when a medicine you depend on suddenly isn't available. Other brands containing gliclazide at the same 30mg modified-release strength are generally considered comparable and could reasonably substitute for what you were taking. Since diabetes control needs to stay steady, please have your doctor or pharmacist confirm the switch and check whether your dose needs any adjustment when you change over.