One possibility is to get a carradice saddlebag. Some of them are pretty large and can hold a lot. That may be your best choice because there is not a lot of heel clearance on this bike for panniers. Calhoun cycles has a pretty good stock of carradice stuff and that's local to you:
Calhoun Cycle Shopcast
There are racks that mount to a seatpost that can hold up to around 20 pounds,
https://www.rei.com/product/697096/t...c:cse_PLA_GOOG
Those won't be as sturdy as a rear rack. You can use p clamps for the seat stays and adapters are made for a monostay,
http://www.amazon.com/SunLite-Sunlit.../dp/B01DDWDZFS
Personally I'd go talk to Calhoun cycles (they've changed their name to Perennial cycles) and see about a large carradice bag with a quick release. Those bags are as tough as door knobs, waterproof, and hold a ton of stuff. You will also avoid any problems with heel strike as well.