HD has the Sprinkler supplies but it's all 1/4", same as John Guest. Depending on what your looking for they may or may not work. (Valves, line etc they have, haven't found bulkheads)
Try calling Aquabrew Coffee & Water Services at (250) 861-5515. I know they have John Guest fittings and I'm sure they would sell them. Not sure what fittings they have though.
or
http://www.shopbwirrigation.com/ you can order them online here.