Based on the fantastic spectra cartridge designed by James Tipton, I've modified it to take full cartridges of film and fit a little more snugly, removing the most tricky aspect of reloading my spectra.

Required Materials:

• Conductive copper tape
• 2x 3.2v 10440 LiFePo4 Rechargeable Battery (if you want to use itype)
• Battery contacts and electrical wire (if you want to use itype)

Required Steps:

• In some spectra cameras there is a plastic piece in the film door that prevents 600 cartridges from being accidental inserted, this just requires trimming back and won't affect the camera negatively at all.
• In some spectra cameras the flap on the film and the shiny black curtain inside both need snipping off the film pack after inserting into the camera, I've done this several times and it usually doesn't cause any light-leak if you take care.
• The rollers on the spectra camera weren't designed with 600 film in mind and may need some adjustment to spread the chemicals fully but you should still get some decent shots right away.

Building the Adapter:
To accept 600 film, there are pads on the bottom of the adapter with holes reaching through to the top, simple run conductive copper tape across the pads, up through the holes and form a little bump of conductive tape in the space above to meet with the contacts on the bottom of the 600 film cartridge. 

To accept itype film, purchase two rechargeable 3.2v AAA batteries and install them in the space to the right, wires can run through the channels provided to contacts on the bottom of the adapter.

That's it! just pop in a fresh pack of film, remove the door and you're away!
Happy shooting!