I did that same mod johnr - except when went a little overboard and added a lighted shutoff switch for the second heater. Which was dumb - I never use the second switch.
It's been a few years but I think I bought all my stuff at YardandPool. but I bet Amazon has everything these days too.
Yard and Pool has every part of a Bradley you can imagine.
http://www.yardandpool.com/bradley-smoker-replacement-heating-element
Thanks