how to generate +5V\2ma from a -90V\1A floating dc\dc ...?

hi,
as wrriten on the subject,i have a dc\dc that supplies -90V/1A,and i need to supply also +5V\2mA,on the same ground.
i thought on linear regulator,to save space & money...but how should i connect the ground between the -90 and the +5V...? (THEY MUST BE ON THE SAME GROUND !!!)...?
(DC\DC solution has a minimum load more than 2mA,and it cost more than linear regulator)
also i regulate the voltage to -5V,is there any switch capacitor from -5 to +5v ?
THANKS
Bull

Tie the reference terminal of -90V and ground of 5V together. This will be your circuit ground. The circuit would be like this:

(+)------------> +5V

(-)
========> GND
(+)

(-)------------> -90V