Kiddie Town has many patterns and styles for BundleMe. Otherwise you can get some from ToysRUs(BabiesRUs)
We got the Columbia one-piece for our son last year, but he was sweating like crazy coz one-piece is too hot for indoor or in car. It's only good when the kid is playing a lot outdoor. You probably have to wash it quite often too because inside is stained with sweat and outside is stained with dirt.
This year we bought two pairs of Columbia snow pants and just match them with some stylish warm down coats coz he's playing outdoor alot at daycare.