Answer: Most of the Japanese maples in the dissectum group are slow growing but actually mature much larger than three feet, so I am not clear on the mature size of the plant you need. That makes it a bit difficult to make suggestions. In any case, I can't think of any tree that would be only three feet tall at maturity.
You might be able to use one of the lacy leafed elderberry shrubs such as Sambucus canadensis 'Laciniata' with feathery foliage somewhat reminiscent of a Japanese maple. It would need an evenly moist soil, though, to handle that afternoon sun. You would also need to prune to keep it small. Its normal size depending on the growing conditions is between 5 and 12 feet.
If you need something that would stay at about three feet tall and wide, you might look at the summer blooming spireas such as Spiraea x 'Fire Light' which has excellent spring, summer and fall color as well.
There are many dwarf shrubs that you could consider using, but your selection would depend on the size, the soil type, the length of time it is sunny, and if it is a windy spot in winter or not. Your local county extension and/or professionally trained nursery staff should be able to help you identify plants that would do well in the location you have in mind, based on a more detailed understanding of the planting site. Then you could select the one you like best from those.
Good luck with your new planting!
Q&A Library Searching Tips