Actually narwhal, the rates are much better for 5 minute jobs than any other duration. As they get longer, the rate actually gets worse. You'd get almost as much by doing 5 minute jobs for an hour as you would for one single 8 hour time. Whenever I'm sitting at the computer I have all my buildings running 5 minute jobs non-stop, the only time I use a longer duration is when I'm going to be away from the computer for a period of time longer than 5 minutes.
I'm struggling for coins more than supplies.
To answer the OP, no, there's no other way to get supplies other than quests and production buildings. You'll just have to be patient and do a lot of clicking. Try and get the buildings with the best production rates for their size. You'll see most of the top players with tonnes of blacksmiths. Although fruit farms have much higher production rates, they are very big and not practical once you start having to cram things in. Blacksmiths, on the other hand, are only as big as houses.