My apologies for the delay in getting back to you. I was at lunch, and then I needed to research and find the exact parts you need.
What you can try to do, is use a pencil, or a sturdy ink pen
And if you have found the lock thats broken.. ( probably on the left side )
Stick the pencil in and push the lock back, the pencil will probably be straight up by the time you lever it back to open the lock.
Then, slide the ink cartridge in. When it gets so far down, its going to try to close the lock onto the pencil. Keep sliding the ink catridge down while you remove the pencil.
That should allow you to get the cart in place with the lock in its proper position. While this isnt a permanent fix. It will get you printing until that cartridge runs out of ink.
As far as replacing the locks. The word document I sent you earlier contains a in depth step by step instruction on exactly how to replace the locks. Its a long process, but doable. You just need the locks. You can order them here for 30$ http://amzn.to/1LwWrsi
I doubt HP sells them cheaper, if they even sell them at all. ( Probably around the area of 69.99 from the MSRP) Amazon is about half the usual cost for that part.
If you have further questions or concerns, let me know!
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Senior Technician and Network Switching Systems Operator / Maintainer.