You can MAKE pure oxygen at home
I did some research about oxygen and it is cheap and easy to make it at home. If you mix Hydrogen Peroxide with a little Manganese Dioxide (a black powder used as a pigment to color ceramics and pottery) it will fizz for a minute, and give off pure oxygen! You can get a 3% solution of H2O2 (Hydrogen Peroxide) at any drug store or super market for about $1.60/qt. You can get MnO2 (Mangganese Dioxide powder) on ebay for $4 per pound (plus $6 shipping) or if you can get down to National City, you can buy it at "Freeform Clay & Supply" ((619) 477-1004) for about $3 per pound. A pound would be several lifetime supplies, because you can get enough O2 (oxygen) to ship an octopus by mixing about one and a half cups of H2O2 with about a half teaspoon full of MnO2.
For the nerds:
The MnO2 acts as a "catalyst" which causes each molecule of the H2O2 (which is made of 2 Hydrogen atoms and 2 oxygen atoms) to break off one oxygen atom, leaving H2O (water) and a bunch of oxygen atoms, which pair up creating oxygen gas (O2).
If you mix these two things in a closed plastic bag, with one end of a tube in it, and most of the air pushed out, you can put the other end of the tube in another bag with some water, an octopus, and most of the air pushed out. Then just let the oxygen flow through the tube and fill the octopus bag. Cheap, and easy!
Safety:
1) Only use the common 3% Hydrogen Peroxide. Highly concentrated solutions of Hydrogen Peroxide (like 30%) can be found at chemical supply stores. That stuff is dangerous to work with. The 3% stuff is relatively safe, but it will bleach the color out of clothes (or your mom's good towels!) and burn your eyes if you splash. Just read the cautions on the bottle.
2) The powdered Manganese Oxide is a very fine messy black powder. Treat it just like the powder you get when you sand heavily rusted iron. Don't eat it, don't breath the dust from it, and don't get the dust in your eyes. Use a WET paper towel to clean it up, never a broom or any method that will let the dust get airborne, and don't use it in a breezy place. It can be toxic if you breath the dust over a long period of time (months?) so just be careful with it.
3) When you mix these two things it will fizz a little, and give off a little heat (that's why you use the 3% stuff). Not enough to burn you, or melt the plastic bag, but don't be freaked out when you feel it get warm.
You can dump the used up Hydrogen Peroxide (now water with a little MnO2 in it) in the toilet.
I tried this last night (without an octopus) and it worked fine. MnO2 is not the only catalyst that will cause Hydrogen Peroxide to give up oxygen, but I think it is the best one to use. Believe it or not, liver (beef liver, chicken liver) also works. So does your blood, which is why Hydrogen Peroxide makes fizzy little white bubbles when you pour it on a cut. I also tried liver last night, since it is so easy to get, and while it worked great, the protien (goo) in the liver caused the fizzing oxygen bubbles to make a foam (like in a protien skimmer) which could get into the tube and into the octopus bag. The MnO2 makes nice clean oxygen without foam. I got my MnO2 by breaking open a flashlight battery, which I do NOT recommend. It was messy, dangerous, and I can't be certain that I was only getting oxygen because there were things in that battery that I couldn't identify. I just wanted to prove that it worked, now I'll buy the pure safe MnO2.
I hope this helps you ship a few bimacs to some eager Tonmo people.