On a modern chain once you push a pin out the swaged part gets sheared off and pushing the pin back in will result in a failure-prone connection; there is not material left to swage it again. Just get a proper master link; KMC, SRAM and Wippermann, if not others, make them. A firm which caters to the recumbent and tandem bike trade will have bulk chains from which they will cut long pieces, but you will of course still have to close the chain. Or you can just get two chains and use two master links to piece in a few links; the shortened chain will have enough links for you to do this many times so you will just need one new one.