Etho, SethBling, and MinecraftAddict have all demoed long period clocks using hoppers and comparators that were added in 1.5.
I'll explain Etho's design since it's fairly simple. Set up an RS-NOR latch using the new block of redstone: put down two pistons facing each other with a two block space in between, and then plop down a redstone block. Cap off the ends with just some redstone dust. These are the inputs for the latch.
One one side of the RS-NOR latch, put down two hoppers feeding into each other. Then place comparators coming out of the hoppers next to the pistons, and have them power a block.
When the hopper has items, it'll power the block, powering the redstone dust, powering the piston. When first starting, you'll put items into one hopper (H1), and the other will be empty (H2). Since H1 has items, its piston is powered, pushing the redstone block next to H2. H2 is now powered, so it can't empty its items into H1. H1 empties all of its items, causing its piston to become unpowered. The H2 piston extends, causing H2 to become unpowered and H1 to be powered. Items now flow back to H1.
You can pull your clock signal from one of the two spaces the redstone block will be to power your command block, or just put your command block right next to it.
In all, the clock is 6wx2dx1h, plus outputs. Much smaller and less expensive (although expense doesn't matter in creative) than your current setup.
There's also some details about this type of clock on the Minecraft Wiki.