If you want to stick with the bar layout, the 3-blush-pan GlamTech palette is probably your best bet. There will be a lot of space at the bottom/top (depending on how you position things), though, because the pans are only about 1.5 inches tall, and the palette is 2.36 inches tall.
The 12-pan 36/37mm one (I can't seem to find the dimensions for this size) might also work if you wanted to go with two rows of six shadows each.
[Ugh, the links posted in a spectacularly ugly manner, so I deleted them. The palettes should be easy to find on the GlamTech page, though.]
Note: I used my Naked 3 palette to figure out dimensions. Those pans are about half an inch (13mm) wide and 1.5 inches (36mm) tall. I may or may not have done the layout calculations correctly, though!
ColourPop has cheap 12-pan ($7) and 24-pan ($10) palettes without clear windows, too, if you were just looking for a way to get the Naked shadows out of the bulky UD palette.