Where can I find source data for the graph of metric expansion over time, as shown in this ESA web page? This web page from ESA/Hubble, shows the size of the universe over time. (I know that "size of the universe" is a gross simplification and open to multiple definitions and ambiguity, but this kind of graph is roughly what I'm after).

But no source data is cited. This is the closest I can find to what I'm after - where can I find source data to match this graph?
I was hoping a physicist might answer this, as I'm just an enthusiastic armchair scientist whose undergrad calculus was 30 years ago. But as no one else has had a go, let me try an answer. 

The graph in the web page is a simplistic and somewhat exaggerated representation of the evolution of the cosmic scale factor a(t) over time. You can derive the "source data" yourself using the following metrics for the three distinct periods in the expansion of the Universe, since the only variable is t which in this case is the age of the Universe. The scale factor a(t) is dimensionless.

For the earliest period of the Universe up to about 47,000 years after the Big Bang, the Universe was dominated by radiation. The evolution of the scale factor in the FLRW metric for this period is given by: $$a(t) \propto \sqrt t$$

After that very brief time (in cosmological terms), matter took over as the dominant factor in the Universe for the next 9.8 billion years, and the evolution of the scale factor is given by: $$a(t) \propto t^{2/3}$$

Finally, the Universe in the current period is dominated by dark energy, and the evolution of the scale factor is given by: $$a(t) \propto exp (Ht)$$
where H is the Hubble constant.

In practical terms, if you'd like to generate a graph similar to that in the web page, you can set $t_1$ = 13.79 Gyr (i.e. the current age of the Universe). I found that the first era of radiation domination is so short that it's not worth including in the graph. 

Here's my simplistic rendition: