Fluval U2 filter

Please bear with me, here is a little history. So about 5 years ago I rescued 2 very large goldfish and they came with a 2 or 3 foot tank and a filter that was not adequate (a stingray 15 i think) so I got a fluval U2 and kept the stingray in there for extra water flow. I re homed the goldfish to a friend that had a pond and the tank was way to small for them as they were roughly a year old, i will add a picture if i can find one

I have just recently found the U2 filter again and i'm ashamed to say along with all the old media... So after a lot of cleaning I tested it (despite some missing parts) and it still works!!!!

And finally my questions:
I am missing the mounting bracket, so is they anyway that i could DIY a new mount bracket for it?
I am also missing the air flow valve, would this be a problem in the future?
I am able to "borrow" some biomax of my sister for the new media but is they anywhere i can get the foams cheaper then local pet stores?

You can buy new brackets from Ebay, and other on-line shops. I know this will be more expensive than making a DIY bracket but you don't run the risk of it falling down. And with a DIY bracket you run the risk of noisy vibrations.

If by air flow valve you mean the venturi, you don't need to use one.

You need sponge that fits snugly so that the water can't creep round the edges and has to flow though it. You could buy a cheaper sponge that is larger, then use an old sponge as a template to cut it to shape.
You don't need to use the poly-carbon pads, just buy a length of filter wool (filter floss) and cut that to shape. Filter wool gets clogged quickly and won't go back to shape after washing; buying a sheet of it is cheap enough to replace it every few weeks.

Ah i didn't think about the filter falling and the noise, so i will most likely get one off ebay. Thanks for the suggestion on getting a larger bit of foam and using the wool instead of the carbon things. Hopefully this will bit much better then my current filter.