This circuit is from Mullard 1969 documentation. The circuit operates at a relatively high supply voltage and has a 10 Vpp output. The transistors are of the time, but admit equivalents.
These days the unijunction transistor (UJT) is not common, but IF you have one you can mount this...
The coil L2 has 64 turns of wire 28 or thinner wire in a 1 cm form coreless and L1 10 turns on L2....
We show only one of the channels of an excellent audio preamplifier with the LM382 integrated...