There are several brands out there, and prices are all over the place...but I like the ones from GreatPlanes
Great Planes ELECTRIFLY Parts and Accessories
Part # GPMM3114
4mm Gold Plated Bullet Connectors - Male (3)
Price @ my LHS $2.99
R/C Racing since 1985 ~ Santa Maria, CA (Central Coast)
2001-2012 - South-West Tour R/C Oval Series - R.I.P.
...will the SWT be revived? Time will tell, but we ARE returning to the VELODROME in 2016