A new carbide bit, and cutting oil and drilling those holes won't be as hard as you think! Use a variable speed drill, and go at a medium speed, with decent pressure. Use plenty of the cutting oil. When you feel you are going to punch through the steel back off on pressure and speed so it doesn't grab when you break through. Also, a punch and hammer to give you an indentation to start drilling so your bit doesn't wander.
If you are dead set against bolts, I've had good luck in using Lexel adhesives.
http://www.amazon.com/Sashco-13013-2-Lexel-5-0-Ounce-Clear/dp/B0012DIUYW
That's not an ad, it's just the first link that popped up when I searched for the product. I don't have any connection to amazon, or lexel, other than the lexel being the brand my boss purchases for me to use.
Hope that helps some.