well what do you know, I emailed the guy for that LIMN battery from ebay, and I already got a response from them.
apparently the batteries are custom made, which "takes 5-7 working days to make and another 8-10 working days to reach you after delivery".
and since we're talking working days here, I could expect at least 2 weekends in there for a total of 21 days, maybe more depending on actual shipping time.
so i'm now leaning towards that 48v 30ah battery kit from battery-matrix.com, and I might just pull the trigger on that one tonight.
i'll run through all my saved links one more time and if something doesn't change my mind i'll have that on it's way tonight. then i'll probably order one extra 40152 battery to keep as a spare, in case on should fail.