Answer: I think you are seeing Magnolia soulangiana, either the species or a cultivar of it. The mature trees do tend to take on a slightly cascading look and the blooms are darker pink outside pale pink to white inside. There are many cultivars. Here is some information about it and photos: (You may need to cut and paste the complete url into your browser to make it work correctly.)
Here is the Monrovia catalog description: Beautiful lawn tree with huge, saucer-shaped white blooms, pink on outside, on bare branches in late winter into early spring. Spectacular show on spreading, multi-trunked form. Terrific anchor or frame plant for landscapes. Deciduous. Full sun. Fast grower to 20 to 25 feet tall, 25 to 30 feet wide; smaller as a shrub. Cutting grown.
Your local nurseries should carry some, if not you might try mail order. Here are some mail order nurseries that might have a selection:
(These are listed in no particular order.)
Best of luck with your search!
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