It looks like I fumbled the numbers above.
To get enough LED current, you need a charge pump with a coupling capacitor in the nF range.
Provided you aren't running it right at its abs.max. input voltage, tapping in at the earthy end of the existing snubber should work OK. It only needs three extra components + the LED, one BAT54S dual (series) Schottky diode, and a resistor and capacitor to smooth out the LED current a bit.
*DON'T* use a LED with a high Vf (so not blue or white) as the extra voltage on C7 directly increases the stress on the Lx pn by decreasing the effectiveness of the snubber.
LTspice sim attached.