I noticed you haven't gotten a straight answer to your question... The best way to get a big female is to find one in your area that was a pet. check the classifieds... I've found several this way in the last couple months.
on kingsnake, big females are starting around $350 I'd say I've only seen one that was in the 3000 gram range and they were asking $1000. I've seen a couple that were in the upper 2000s, they were in the $700-850 range.
Personally I wouldn't drop that kind of money for a normal female, just keep your eyes open and you'll probably be able to pick a few up for a fraction of the price. Of course if you've got a high priced co-dom that is ready to go, it may be well worth it to pay whatever anybody asks!
The bp market is so strong right now that it is almost worth it just to buy baby females, grow them up and sell them for a big profit each year... but that's not the fun part!
Anyhow, good luck with your projects.