Your right it will be hard to find Lardizabala viable seeds.
I have no experience with amelanchier and dead mans fingers.
Dead mans fingers looks like a curiosity collector plant rather than an usefull fruit tree.
I got an Akebia wich is related to dead mans fingers and i consider it a curiosity also,not an usefull fruit.
If you can find at the nursery and if they do well in your area i reccomend the mini kiwi ,,Issai,, or ,,dr Szymanovsky,,.These are good fruits available for cheap at supermarket seedling place this time of year.