We had the same problem on our bavaria 34 which we purchased from Opal, New in 2001. Our solution was to manufacture our own drainage kit from 4No stainless steel bolts and 2No lengths of clear plastic hose of the correct diameter to fit snuggly onto the threads.
    You can use any size of bolts; from memory we used 8mm. The bolts were simply drilled out so that they would allow the passage of water. 2No bolts had their heads turned, in the lathe to form the same shape as a sink outlet and the other 2No bolts had their heads turned in the lathe to form a small gargoyle. The deck moulding was drilled Port and Starboard, to take the inlet fitting, at the deepest point of ponding. We then countersunk just enough to allow the inlet fitting to be flush with the gell coat. The outlet fittings were positioned so that they drain below the gas locker on port and in a similar position opposite on starboard. We then simply locked them in place with nuts and washers, having applied a bit of sealant, and connected with the flexible pipe.
    They are a bit on the small side so sometimes block, but we keep a length of wire in the toolkit to free them off. Once or twice a year does the trick.
    So if your boat is outside of dealer warranty, there is a simple solution and it has worked well for us for 8 years.

    Hope this is of help.