A real battery store should be able to sell you “Battery Acid” in a one quart or one gallon box. These boxes come with a dispensing hose attached…Handling the acid just takes a little common sense…
But you have another problem…You must dump out all the diluted electrolyte from the battery before you can add the fresh acid…What do you do with THAT?? Nasty stuff to get rid of…Maybe the place that sells you the acid can help…