Make electronics - charles pratt - experiment 11
It doesn't work because they are radically different components.

The PUT is a strange beast; it's like a hybrid between a bipolar junction transistor and an avalanche diode. It has non-linear behaviour: once the current flowing through it has gone above a certain value, its resistance collapses and it becomes "more on", until the current falls much futher than the trigger level.

This lets the oscillator work: it charges up the capacitor, until the trigger of the PUT is reached, at which point it discharges through the LED until the current falls below the turn-on point, and the PUT turns off again.

In some ways this is quite a lot like the 555: you could almost just substitute it with the "discharge" and "trigger" pins wired to the capacitor-resistor junction and the "threshold" pin wired to the 15k/27k voltage divider.

(For practical purposes the 555 obsoletes the PUT, which is why everyone is suprised to find the PUT in a book that's in print today)

In your circuit, the MOSFET will just adjust itself into its linear region such that the gate-source voltage is at the turnon point, and stay there. There's no nonlinearity to produce oscillation.