Here is my version. I do not like the one you posted, because it is overly complicated, and it takes too long to discharge the timing network if the power is momentarily interrupted. Mine resets in less than 1s. I intended it to be used with a 12Vdc relay that has a coil resistance of 100Ω or more. The parts cost per Digi-Key is less than $1 not counting the relay. If you need a longer delay, I would say that an upper limit on R1 is 4.7megΩ. C1 should have low leakage.