One of our premier members, LittlePixel, is a avid Raleigh Twenty owner/restorer. Here is some photo links of replacement bolts & fasteners that he's done to replace the stolen ones on his Twenty(s):
New bolt seated on washer
http://www.flickr.com/photos/littlepixel/234211841/
New frame bolt
http://www.flickr.com/photos/littlepixel/234212239/
Tightening new custom bolt
http://www.flickr.com/photos/littlepixel/234212201/
I am now planning on going to a good local hardware store myself to always have some spare frame bolts & fasteners (wingnuts, allen heads etc.) on hand for my own Twenty. Thank you again Little Pixel for showing the way.