Try Consolidated Bearing Company (CBC), they're a chain, or:
A.B.C. BEARINGS PTY LTD
Head Office 11 Cullen Pl Smithfield(02)9725 5944
Brookvale 16 Powells Rd 2100 (02) 9939 2555
Silverwater Unit 7/ 24 Vore St 2264 (02) 9648 0755
I got a bearing for my A/C idler puller (4AGE) for about $8 from ABC at Brookvale. The bearing was held in the pulley with a circlip. Is that the same as yours? If you can take the bearing out I'm sure (pretty sure) a bearing shop could match it up, but if you go there and say I want one for GZE or GE alternator tensioner pulley then they will probably have NFI