I usually get stuff like that from Summit, since their prices are reasonable and they offer free shipping. eBay is also another place, but just be careful. Check out the sellers before you part with your hard-earned cash.

In your area, I HIGHLY recommend Jim Grubb's Motorsports. They are the best machine shop I have ever run across, and are very knowledgeable and very open to sharing their knowledge. They can track down anything you'd need, but you'll probably pay a little more for it to get it through them.

There is a decent racing shop in Simi Valley, but they are not dedicated to Pontiac, so getting anything in a hurry (or getting good advice from them) isn't going to happen. But they can be useful for generic stuff like braided steel lines, Holley carbs and fittings.