Ok, clear.

They are the same as the first generation of the Picco P7R.
They are NOT the same as the IDM, because IDM swapped to Picco only after Serpent and Picco solved the issues with the first generation of the engine.
The first Picco based IDM is based on the Picco P7R EVO 2, like the Mega DSII is.
A year later Picco made a running change in the piston without changing there engine name, but Mega called this the DSII+.
The Picco EVO3 / IDM EVO3 / Mega DSIII all 3 share the same internals....
The Picco EVO4 / Mega DSIV are also the same I think, but I've heard rumors concerning IDM...

So, I hope you can find spare for the engine, they are still there somewhere, but not easy to find I think....
Contact a Picco dealer, to have the biggest chance.