it is an uncommon cultivar in bonsai (not all dwarves are great for bonsai), and you are therefore going to have a very hard time finding a specimen on its own roots
i have a few of these. they can be air layered, so one option would be to buy a grafted specimen with appropriate movement, and air layer it. I do not recommend this.
if i were you, i would look for a flowering (grafted) specimen, and propagate it via seed. these make nice landscape specimens (mine need full shade as of noon). by propagating via seed, you can choose a vigorous specimen with the characteristics you desire which is a great way to find material with good bonsai-potential. it is incorrect to view this as a compromise as opposed to getting the 'real thing'. this is how many 'cultivars' were selected and named, and you'd simply be doing the same thing.