Biglots, Family Dollar, Dollar General (Everything's $1 stores won't have much, if any)... Chinatown is usually great... ebay usually has better quality ones if you know where to look
http://search.ebay.com/_W0QQsassZchimungmung http://myworld.ebay.com/decepticonzero/ http://search.ebay.com/search/searc...=compare&copagenum=1&coentrypage=search&fgtp= http://search.ebay.com/_W0QQsassZblackgaine I'm sure there's more, but those are places to check first...
There was a website that had about every TF ko available, including the white Cyclonus etc, cant remember the name of it though
Try your local swap meets and flea markets. The ones held at the local community colleges and fairs in So. Cal are where I go my KO G1 combiners as well as a KO Abominus!