Suggest a regulator which can generate 450V output with 1mA output current from a source with minimum 5V to maximum 12V input.
Regards & Thanks
have you checked out the LT3751 yet?
Linear Technology - Product Page
Its intended to charge capacitors to large voltages and offers plenty of power as controller. When 450mW is all you're asking for the integrated parts like LT3484 could be worth a look, too:Linear Technology - Product Page