The GD Idler pulley bearing uses a NSK 6203-DUL1B which is apparently OEM only, when getting a 6203 from the bearing shop should you specify light contact rubber seals or full contact seals?
Apparently the shaft size on the 6203 can be specified and on the Fit the 6203 has a 17mm shaft size/inner race - does that seem correct?

 

Luckily I took a pic of the bearing when I last had the idler pulley off, seen below:

 

I replaced mine this past summer too and had to get the part direct from Honda: 38942-PWA-004 Pulley, Idle $43.52 1 $43.52

I used hondapartscheap.com

 

I just pressed a new bearing in, was a pretty simple job with a G-clamp and a block of wood, I used the old bearing to press the new one in.
You need a 6203 2RS (it must be a bearing with 2 rubber contact seals), I used a Timken bearing.
The bearing was $5, so great value for money if your existing pulley is still fine other than the bearing.