I found some Sikaflex 252 at Northwest Trailer Repair in Fargo, ND. They had it by the case and it was about 18 months ago when I bought it. I think I paid $7 per tube and the stuff seems to work great. We were putting aluminum onto steel.
Northwest Truck & Trailer
www.wallworktrucks.com
4020 12th Avenue North
Fargo, ND 58102-2910