I think Rapps still got them. that list is current I think. And 150 gallons will do just fine for a gatf. So what if they grow 100 feet, arapaimas, gars, arrows all grow too big for most tanks but we still buy em and enjoy them while we can. It seems most of these fish die before they hit the too-big-for-aquariums-size anyway.
I hope you get one, theyre pretty fun fish to keep.
For 100.00 you might want to snap a picture and post it... I have a feeling it's one of the other species of ATF... But very possible as I have purchased GATF sold as VATF