It's quite expensive, but there are breastmilk banks throughout the country. Another option, something that my friends and I did, which makes other squeamish, is have a friend pump and donate, or wetnurse for your baby.
Whenever someone in my circle of friends needs a babysitter (and we're *all* against artificial nipples as well), if another mom is a nursing mom, the sitting mom will nurse the baby. Some babies won't allow it, but most don't care as long as they *know* that other mom... There was a time when I went to a get together with all of us moms and one of the moms was actually drawing near the end of nursing her son (he was 3), and she was really in pain from engorgement. I let her nurse my baby (who was like 3 months old at the time) and she got relief. Unfortunately I was only there for a few hours and she had to just hand express when we weren't around, but you get the idea.
If getting milk from another source is an option you are comfortable with, look into it.
