I have been using the ‘Uniden Mystic’ for the past ten years. A waterproof DSC-VHF with a mapping GPS and a large screen LCD. The closest thing to a plotter that you could hang from your swimming aid. IMHO the perfect solution for a Wayfarer. Unfortunately it is no longer available, I can’t even get spare batteries for it. The Mystic is sorely missed.
But if you can find one used with a good battery, go for it!
The Standard Horizon HX851E I bought last year is a much better build quality but it lacks a map/chart.
As for batteries, I carry spare pack and the device does not need to be switched on all the time. A quick check and than its back to the compass. That way the battery will last days and there will still be enough power left to send a DSC-distress or a Mayday message.