we bought some for our jan trip with our son, they were great (until he took it in the hot tub with him...that wasnt so great)
we got them on ebay, brand was cobra 8 mile radius i believe (could be 4, but i think 8) we only paid like 15.00 plus shipping or less, but cheap. we could have gotten 3 of them for 8 bucks more but i didnt think we needed them, now i wish we had, we all wanted to carry one then the other one drowned and we had only 1, which ofcourse was worthless
search ebay, the guy had a great rating and sent them to us in less than 3 days. He was great, and had a 99% rating with thousands sold.