Hi Dave
Have you tried High Planes & Red Roo both from Australia
As the Heller Mirage IIIC/B is used as a base for building our much loved RAAF Mirage IIIo, both these Australian companies do resin ejection seats, cockpits & full IIIo conversion sets that might be of use for this kit. I've used all of these bits in combination with the Eduard PE set that you mentioned to make my RAAF Mirage Kits.
http://www.redroomodels.com/
Mirage IIIB conversion
http://www.redroomodels.com/conversions.php?conversion=354
Mirage IIIO conversion
http://www.redroomodels.com/conversions.php?conversion=353
http://www.hiplanes.dragnet.com.au/
Mirage IIIO/B Martin Baker Mk4 Ejection Seat
http://www.hiplanes.dragnet.com.au/new/ima...C4803_large.jpg
Mirage IIIO/B Martin Baker Mk6 Ejection Seat
http://www.hiplanes.dragnet.com.au/new/ima...C4804_large.jpg
Jim (from the great southern land)