the e-retailer I bought the replacement buckles/adjusters was:http://www.strapworks.com/
Just cursor down the left menu to 'side-release buckles' (metal)...
the company has both aluminum and nickle buckles.
You can also choose for a few extra cents (about 25 cents), which color you want anodized on the buckle and also if you want shiny or matted surfaces.
They ship by priority mail, my buckles arrived three days after I ordered them.
Don't forget that the tramp straps are 1 inch wide...so order the 1 inch buckles.
You will have to get new 1 inch nylon straps to replace the straps which wrap around the tramp rods. The old straps are sewed onto the rods and have to be cut off.
The metal buckles should be inspected for corrosion like all other metal parts on the Hobie. I don't know how long the metal buckles will last being immersed in salt water. But I believe that the plastic buckles which are resistant to corrosion tend to slowly craze from UV sunlight.
I did not replace the plastic buckles which did not break...I wanted them to still be the weakest link on the tramps...rather than the amas.