Originally Posted by Mikmay
...I also think the op stated he has 2 trikes which I don't think you will find any fg trailer to hold them but I do have a solution , buy 2 HC1s lol
Since they are trikes, I see no reason both wouldn't fit into one HC1 if they were loaded side-by-side in opposite directions. But there wouldn't be much space left for beds, galley, etc., so it rather defeats the point of a travel trailer.
I believe Chariot Manufacturing
makes some nice molded fiberglass cargo trailers in various sizes. Might be able to finish one out according to your needs.
Again, the OP hasn't told us what he wants the trailer to do, besides carry the tricycles…
Personally I like Floyd's suggestion best. Start with an older 13'er with a flat (or mostly flat) bathtub floor and put it on a larger trailer, or have a custom frame fabricated. The photo shows a Hunter Compact Jr. on a custom frame with an extended tongue to carry a motorcycle. With the trikes stored outside the trailer, you'd have full use of the trailer at all times. If security or protection from the elements is important, you might be able to find or fabricate some kind of lightweight shell to cover the trikes.