I've got the Lee 20lb. bottom pour and love it. I bottom pour for regurlar bullets, but for the round balls and hollow base single cavity bullets I use the ladle with better results.
The lee two cavity round ball moulds they sell at Midway are about 17-18$ and work great, and they don't have a nib at the sprue, just a flat spot. My only complaint is that there not six cavity.
I have a hard time finding pure lead also, but if you pick through wheel wieghts and get the stick on type most are pure lead or close enough too it. I've run into a few zinc stick on, but there easy to distinguish. Just flex them and you can feel how soft they are. Save the regular wheel wieghts for regular bullets, they work great.
Heck even if you have to buy your pure lead you will still be money ahead casting, though it'll take longer to pay for the molds and lead pot.