Relationship between spectral efficiency and PAR
I'm with BlackMath here – a PAPR vs SE graph makes little sense, since you would be denying the differen BER at fixed SNRs you'd get.

Let me give you an example:

256-PSK has a PAPR of 1 – the "best" you can get. It's way lower than the PAPR of 256-QAM. 

Both have the same spectral efficiency (which doesn't depend on the constellation shape at all, but only on the number of constellation points). 

You would, however, never use 256-PSK, though, because it's terribly low on distance between constellation points. 

Since you could define a PSK with any number > 1 of constellation points, and any PSK has PAPR of 1 ("doesn't get any better"), that graph would be mighty boring.

Aside from PSK, there's, for spectral efficiency-sensitive applications, only QAM (and things that are pretty much QAM, e.g. Amplitude shift-PSK). So, that graph, if only considering constellations that "make sense but aren't PSK" would in the end only compare different power-of-2 QAMs. There's little surprise in that – you simply get the PAPR of these QAM constellations – which is a bit ugly to calculate analytically, but holds little surprise: the higher the number of bits, the higher your PAPR in a QAM. 

Instead of hoping for a constellation, I'd simply use e.g. Python to give me grids of $2^n$ points centered on 0+0j, and simply calculate PAPR on these over n. That's less than 50 lines of code :)