Is there a small (max 5cmX5cmx5cm), inexpensive test device or card on the market that I can use to test my phone line at the NID without using a telephone? This is important as I have a cordless.

You can use your cordless at NID. You just need Extension cord, The base unit and transformer plugged in. then test phone. I'm still looking up 5cm(How much is that in feet?)

This: might help:

KC9ASI - How To Extract the LED from a "phone line tester" (http://www.qsl.net/kc9asi/led/index.html)

You can leave intact for your use.

You can use your cordless at NID. You just need Extension cord, The base unit and transformer plugged in. then test phone. I'm still looking up 5cm(How much is that in feet?)
5cm is about 1.5 to 2 inches. So I'm looking for a device that's no more than a small deck of cards.

Have you checked Radio Shack?

Goto: Gardner Bender Modular Dual Telephone Line Tester - GTT-200 at The Home Depot (http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay?jspStoreDir=hdus&catalogId=10053&marketID=401&productId=100027519&onlineStore=true&locStoreNum=8125&keyword=phone+line+tester&langId=-1&searchRedirect=phone+line+tester&storeId=10051&endecaDataBean=com.homedepot.sa.el.wc.catalog.bean s.EndecaDataBean%4012018939&ddkey=Search)

See: Gardner Bender Modular Dual Telephone Line Tester

Model GTT-200

$10.79/Each

Hope this helps. These are handy!