Being left-handed, and preferring to buy new rather than second hand, necessarily means buying online unseen. Having started playing in my early 40s means I was old enough to have a reasonable idea of what I liked from the start - no Fenders, no big bodies, no muddy crappy P-style pickup, thin neck, modern sound, 34 inch scale, minimal string spacing.
Every bass I bought myself (as opposed to generous presents from @Happy Jack) has been from Thomann, with only one exception (PMT). I've had to send back a couple of defective instruments, which Thomann replaced quickly and with no quibble.
The only bricks-and-mortar shop I can think of, which almost every time I visit has a lefty bass I might be interested in buying, is Wunjo's.