ok, lets look at this from a broad viewpoint.
You already have a jb3. You still need mics, power, pre, and an adc for under $500 and stealthable.
I got an answer for you.
MICS
SP-CMC-2 (at831) = $120
POWER
SP-SPSB-1 w/ bass roll-off = $80
PRE/ADC
denecke AD-20 (inbox) = $200 used
You can use the extra $100 for extras. You might need attenuators for the AD-20. Because the AD-20 sends a hot signal, you might need attenuators to take the signal down a bit so your recorder doesn't distort, but this depends on what you are recording.
Also, for open taping, people have mentioned stands, tbars and the like.
You'd need a cable to run from the battery box to the AD-20, and a cable to run AD-20 to jb3.
That is really the only solution I can think of given your parameters.
good luck!
~schwill