So I am needing to replace the brake pads on my trailer and in looking at the trailer related manuals that came with my boat, I found that you can use the brake pads for a 1997-2000 Kia Sephia which are readily available at auto parts stores. Be sure to get organic, not metallic pads as the metallic pads will rust. See below.

You could also order pads from pacific trailer or other trailer parts sites. Our boatmate trailer uses the DB-35 brake caliper (or at least mine does). Here is the link for the pads. It's actually cheaper than the Kia pads they sell at Autozone.