I'm not sure if it is lazy retailers or what but I've heard the same thing from more than a few places. I would think since Levy is the largest strap and gig bag manufacturer that they would warehouse large quantities of their stuff in the US rather than ship orders from the Nova Scotia plant so that they can respond to orders more quickly.
I think that Levy makes the best "bang-for-the-buck" gig bags and bass straps. My leather gig bag and my F Bass gig bag are among my favorites. And most all of my basses have the M4GF strap on them.
As far as the retailers are concerned and as we all know the majority of stuff that they have is gear to the skinny 6 string folks. So most of their orders are those spindley little straps and short gig bags. As far as online I haven't had much luck. I've emailed several of the big bass shops and not had any luck. I guess they look upon accessories as small peanuts when they budget for their inventory.
I just needed to vent

....but I might have just found an online source.