Bouancy AIDS for kids

We are currently living in Hong Kong and both my kids are avid sailors. One is sailing in the Opti's and about to do the Hk Opti Nationals with over 91 entrants, there are more expat kids than locals sailing. However off the point, I brought last year for both kids new bouancy aids, they use them twice sometimes 3 times a week for long periods of time and I have to say that we have been very disappointed with them, the fit has been terrible, they both find them uncomftable and within weeks they started falling apart. I have searched websites and forums to see if there have been any articles on the best BA's for kids, I imagine there would be a lot of parents who would be interested to read, re safety and also comfort and agility for movement. I need to buy new BA's for both kids but am at a complete loss now what to buy for them, ideally I would like Them to last longer than a year.