transformers for cheap low current flyback supply, +/- 45V ?

I just did a bit of consulting work, on excactly this. customer was concerned they had a wiggly line not a straight line. turns out Ton was about 200ns at min line.... I suspect the wiggle is undamped gate current.

Epcos, Panasonic, Matsushita, Toko etc. make those things. They are hard to buy in small lots. The best way is to buy samples or evaluation kits. .

One of the weak points in modeling programs is dealing with the increased resistance you see at high frquencies. The circuit I suggested gets rid of most of the cross regulation effects from both the leakage inductance and the increased resistance. It doesn't remove the effects of the DC resistance of the coil.

There is a bit of a problem when you go to model it. If you take the usual tack of increasing the resistance to near its AC value, you will get too much droop in the unregulated output. If you leave it as the DC resistance, you will get optimistic results for things like the losses.