I have the VX-5 so the standard Yaesu plug they make works for me, but I know exactly what you guys are talking about. I have another set of Marine/GMRS radio's that do have a very similar waterproof plug like the VX-7, but its 2.5mm and its tough to find anything to fit.
So what about a plug like this that has the correct VX-7 waterproof connector on one end and then the standard 3.5m 4 prong plug on the other end which is basically what the VX-5 plug is. - Ebay Link
There's a couple different ones out there too. - http://www.ebay.com/sch/i.html?_trks...at=0&_from=R40