Check out this link and scroll down to "Used" section(s).
I got mine for about $6usd

Also, insofar as spraying a perfume to try and alert the dreamer he/she is in REM, this is to try and get the person to notice a dreamsign (smell in this case) in the dream and hence bring upon Lucidity!

The NovaDreamer is a unique method/tool and does not need another person staring at you while you sleep (I coudn't sleep!)
The ND is a mask you wear over your eyes and has a set of programmable LED lights and audio alarm (beeping). WHen you are in REM, (the ND detects REM) the lights are signaled and will start blinking a series of flashes for several seconds. The goal is to alert the dreamer that he/she is dreaming and he/she will become Lucid.
Before you go to sleep, you need to strongly affirm that if Anything with Lights appear in your dream, then you will realize you are dreaming, and do a RT.
The flashing lights will appear creatively in your dream as , for ex. car tail lights, fireflies, streetlights, stoplights, disco lights, etc etc etc!
SO it is imperative you do strong affirmations regarding lights or beeping (if u use it) then you will realize you are in a dream!

I suggest waiting on the Nova Dreamer; new model is under development. The old one was sold to some company who jacked the prices more than double ($450.00 ouch!)
Or you can search on Ebay for some deals.
It will probably take some time to get use to, as it does most people. BUt, it is just a nifty tool that at least detects REM, and no other sleep stage.
As with anything, Practice practice practice!

Hope this helps

ofp