Ity turns out I did still have some non-chip CCs, so I went to Simon mall today and bought 19 $500s, then headed toward Milwaukee to visit my mother. The first WM I went to had run out of MO blanks and neither cashier knew how to put a new roll in. They were waiting and hoping that someone in the know would show up, but they were saying at least 20 minutes plus there was another customer waiting for 6 MOs, so I went on to the next WM.
There I was met with suspicion by the cashier who apparently had never dealt with GCs. She called over another cashier who also didn't know how to do the transaction but allowed me to try a few swipes. The swipes were rejected -- I'm sure she was hitting the wrong key, but I don't know which key she should have hit, so I just left. The third place let me have 2 MOs, and I was able to get MOs on the way back home at the first two WMs and then the one in Madison, so it worked out with a little extra effort.