I ordered 2 timing pulleys a belt and stepper yesterday @8:50am from http://ausxmods.com.au/
and with a long weekend coming up I expected them arrive next week but got them today @ 9:50am.
Can't complain about the service or price.
For North America I got mine from econobelt.com who are associated with Quality Transmission Components (QTC) who are also related with sdp-si based on their website http://www.qtcgears.com/related.htm
The econobelt site let me order a smallish quantity (~$100), sent me 2 paper catalogs (huge things - great gear refference material!) and shipped USPS which is a major plus for us in Canada who aim to avoid the UPS brokerage scam....
This was ~ 2years ago so I would hope they haven't changed much. I also liked the way their online catalog was setup - onece I got used to it. http://www.econobelt.com/Timing_Belts.htm
I use Mcmaster Carr for the occasional belt or pulley http://www.mcmaster.com/#xl-series-timing-belts/=i98tyr
I get lightning fast service if I call before IIRC 7pm I have the part the next day UPS ground rates. again satisfied customer.But they apparently do not ship to Canada.
If I was going to build a reprap type machine I would probably look into econobelt.
Tin