360 intake manifold gaskets?

please note im a newbie! so im having trouble sealing up my 360 intake manifold. I have tried several times now and cant seem to stop the leak, i use the two gaskets on the intake ports but i couldn"t find gaskets for the front and back of the manifold so i just have been using rtv....... :/ and that only works for a day or two then starts leaking again. Does anyone know where too get those other gaskets, or some trick, or do i make my own out of cork? thanks alot