It's finally happened. It took a while, but I was able to find the upper level booster tickets from 2003 Fleer Authentix. The last non-numbered card I needed for his master set:
I found it on COMC one day...it was less than $5, and once I double checked to make sure it actually said upper level I snatched it up. So lucky.
Every card of Seneca's that I still need is /100 or less, most /50 or less. So here's where it gets really tricky. But the collection must go on!