Can you even write with 0.35mm leads (the model dvessel bought)? Even at 0.5mm, the only lead that doesn't keep breaking on me is Pentel Ain, and that is impossible to get anywhere around my uni. Do you know monolith?
I bought mine from this seller: Rotring 600 Old Style 0.5mm Pencil Black or Silver New - (eBay.ca item 250290436832 end time 10-Sep-08 10:38:55 EDT)
But shipping is $10, though if you're in the US you might get it quicker. I asked him a question after I bought mine, and he replied in what must have been 2 minutes, so I'm thinking he's a good seller, has plenty of feedback, and a website selling pens and things.
Actually, I didn't even realise that's the model I'd linked him to. I usually use the 0.5mm lead myself. 0.7 feels like writing with a crayon. I don't have a problem with 0.5mm lead breaking, and I write with a lot of force. Just have less lead exposed. As such, I'm afraid I don't know where to get fancy lead varieties, as I'm fine with whatever is around in Staples or wherever I go. Rotring lead is actually really nice, dark and smooth (I got some a while back), but I can't be bothered to buy it constantly. I write so much that I go through it pretty fast.
I do have a nifty lead holder with a trap door like lid that retracts with a thumb button thing though. It kind of feels like using a lighter.
To dvessel, I'm sorry I linked you to the 0.35mm pencil. I'm not sure if that's the one you bought, but if so you might want to contact the seller and change your order to a more easily obtainable lead size, like 0.5mm.