When I bought my H18 I sold the trailer it came with and bought the Trailex trailer. I absolutely love it. It's light, easy to add accessories to, and won't rust (I sail in salt and brackish water 95% of the time). I do plan on keeping my boat and trailer for a long time so to me it is worth the investment.
You can make the H16 trailer fit the Wave, but you will have an oversized trailer. And as mentioned before, a boat for sale without a trailer is a slow mover so it may be wise to get a trailer for the Wave and worry about the H16 when you finally own one.
You could use a flatbed utility trailer for the Wave too.
In the market
Previous boats owned
'74 Pearson 30
'82 H18 Magnum
St. Louis, MO