I think you may be looking for a bottom bracket (spindle + cups + bearings) that screws into the bottom bracket shell on your frame. You can find these at any LBS and most likely one that will work for your bike and crankset.
'84 Trek 850--spinbackle-built, '85 Trek 670 Campy Nuovo Record--project, '87 Trek 560 SS/Fixed--project, '87 Specialized Stumpjumper Comp w/ Deore XT--Specialized-built, '87 Rossin Record, '03 LeMond Wayzata--commuter,
'?? TST Mtn Bike frame--project, '07 Tsunami Tandem--home-built