So I started researching alternatives, and found it at Aquabarrel, another rain barrel vendor. They sell a bulkhead fitting with the valve and thread converter for $22 plus shipping. I ordered one and received a rugged part in the mail several days later.
Start out by disassembling the top cap, screen and tray. Put the barrel on its side.
Step 1: The old spigot
It is very flimsy too. Hence this Instructable.