Check with Gary Swandells in the UK. He sells refurbed NJB3s on eBay and if you ask him to, he'll list a display on eBay with a Buy it Now option. It'll cost you a little over $16, delivered to your mailbox in a padded mailer. Just find one of his other auctions on eBay and use "Ask seller a question" to contact him.
It only takes about 10 minutes to replace a "screen" as Gary calls it. He can refer you to good instructions on how to do it.
Here's some instructions that were posted on nomadness.net:
1- use a needle or straight dental probe etc to tease out the four rubber feet (note each is unique)
2- use the correct size screwdriver to remove the four screws now revealed, plus one in the battery compartment (from memory i use a pozidrive No.0)
3- gently ease of top cover (mind you don't lose the plastic infra red window at the front)
4-ok your'e in now, don't panic, just be careful.
5- on the lower right hand side of the display are two solder connections, these must be carefully (no, very carefully) desoldered. i assume you have a fine pointed soldering iron and some form of de-soldering equipment ie either a pump or de-solder braid !
6-the display is only now mechanically held by the four spring clips, two on each side, gently spring both out on the left hand side using the tool from step 1 and then fiddle the other two out
7- the display is now off the board but still connected by the fpc. gently fold the display away from you so clearly revealing the connector. The darker coloured plastic where the fpc plugs in is hinged at the back where it meets the lighter plastic. Very, very carefully using a suitable tool lift up the front edge (it is on a latch so you feel it sort of click as it unlocks but don't force it you really musn't damage it !!) and this will release the fpc
8- if you only have the glass you must now carefully remove the old glass from the metal backing plate (don't bend or distort it) and stick the new glass back on. only use the tiniest amount of glue absolutely on the very edge at the right and left sides
9-putting it back is pretty much the reverse procedure, just take your time and be gentle