I currently am using a 500 micron D-frame dipnet with a 5' wooden handle from Wildco. I also use a 250 micro mesh sieve, a small wash bottle, a 5 gallon bucket, a bottle of grain alcohol, and some pint-size plastic sample jars. I fill the bucket half-full at the collecting site, work material into the dipnet by hand or kicking or both, then turn the net inside-out in the 5 gallon bucket to transfer the collected material. Then pour the bucket contents through the 250 mesh sieve, and transfer that material to a sample jar by washing down the sieve with the wash bottle. I then add enough grain alcohol to bring the alcohol concentration to about 70%. I find samples collected like that will last at least a week without decomposing, probably longer but I haven't tested. That gives me time to go through them without a rush.
My dipnet, sieve, wash bottle came from Science First. The alcohol came from the liquor store - here in Vermont you have to sign an affidavit stating your intentions for the purchase, not to include drinking it, and you are issued a license for x bottles personally by a rep from the DLC. I'm told in New York State anybody can just buy it in a liquor store, which I might try when I run out. It works well as a humane killer and preservative.
I clean my equipment with Lysol Kitchen Pro spray - because it contains quaternary ammonium, a widely-used disinfectant. It acts rapidly, within 2 minutes, and then I wash it off by dip net, sieve, and waders. The Kitchen Pro product is 'suitable for food contact surfaces' - although emerging evidence suggests that quaternary ammonium products need further study to fully understand risks. For the amount I use, in the places I use it, I am comfortable that it is safe.