the thingy you mention is called a rotor. i fitted one with my paper round money back in 1987 to my dp firebird freestyler,it was made by acs the inventors of the idea and cost me 55 quid fitted back then. anyone calling them a gyro is a new school poofder .

for info on a thingy click... http://www.23mag.com/com/acs/acs.htm

theres loads of bmx's like you mention for no money whatso ever down the tip or salerooms/local paper,i got a mongoose to get me back in the swing of things and it cost me 20 quid from my contact down the local council tip,i went on the internet and they are 270 quid. bargain