Seller Sapphirechild on etsy.com has one BS aberrans in stock for $15 and $6 shipping (I know, super cheap!). Don't know if she'll have more to sell anytime soon. I've gotten a few things from her in the past and she always has good quality and rock-bottom prices.
I got my aberrans from Marble Branch Farms in February for $10 during a field trip with my OS. They've never listed it one their website but they might still have some in stock (probably for $15-20). They also have a few primary hybrids of aberrans if anyone's interested in those for non-project purposes.
I think most of these current seed-grown aberrans are coming from H&R. They don't have any listed in their current price list but they might have enough around for the project (assuming that's what's picked, of course!)...
Philip, I'm intrigued by your suggestion of Australian Dens; which ones are you thinking of? I think kingianum and tetragonum have already been suggested, though as someone else pointed out kingianum can be a reluctant bloomer without a cool period... I'd love to try out a few more of the Dockrillia/Rhizobium Dens, and enough of these are available in the US that importation might not be necessary. I've been told most of them are very temperature-tolerant and generally easy to grow. Shoot, maybe I DO want to join the project after all...
--Nat
EDIT: I forgot, I think Oak Hill listed aberrans until recently, to my recollection for $15 or $20. I don't know if they still have any to sell or not...