Can any one suggest a backpack that will fit a regulator, computer, and BC in it and will fit ALMs restrictions? Does anyone know ALM's restrictions in inches?

ALM has the same carry-on restrictions as the other airlines. If a flight is really loaded they will restrict you to one bag. I use a sturdy backpack that fits overhead or under the seat in front of me. My bcd rides in my checked bags. I also pack toiletries, a swimsuit and light shirt and shorts in my carry-on.

The numbers are 9 X 14 X 22 inches including handles and wheels.
I get everything I need to dive except fins(BC, wetsuit, regs, mask, ect) , take UW pictures and live(shave gear, swim suit, shorts, T shirt etc) for a day or so, in one wheeled carry-on and a camera bag.
I have used a mesh backpack that then doubled as a divebag, but everything sort of ended up in the bottom of the bag and it was bulky and awkward, so went to the wheeled carry-on.

Ask for a seat in the rear of the plane. That way you board first and have a better chance of getting your carry-on in an overhead compartment if it's crowded.

>> Can any one suggest a backpack that will fit a regulator, computer, and BC in it and will fit ALMs restrictions? <<

The small eagle creek duffle works well. Any backpack that you don't OVERSTUFF to a hieghts greater than about 11" or so will fit in the overheads of the MD-88's, forget the DASH-8's. I've reworked my diving backplate/harness/wing to attach my duffle bag (a few grommets here and there, a few SS bolts) and voila' an easy to carry backpack that fits in the overhead storage AND is readily convertible into my diving rig. I get EVERYTHING including fins, regulator (break it down), mask, computer, wetsuit and an entire weeks clothes into one compact bag that fits into the overhead!

Good luck.

Bob