Trailer Frame for 5x10 Teardrop

Where can I find a frame to build a 5x10 teardrop on? I've done a lot of searching, both on this site and elsewhere, and I just can't find a good option.
Harbor Freight and redtrailer have plenty of 4x8, and I even saw a 5x8 one on Harbor Freight's website. Can you take that and just extend the teardrop frame a foot on each side, front and back?
I know that 5x10 is a common teardrop size, and probably what we'd be looking to build so we could fit a queen sized mattress in there (my husband and I are NOT small people!)
Also, I see plenty of trailers for sale with mesh bottoms and side railings. Is it possible to get one of these and either a) assemble it without the mesh and the sides, or b) buy one already built and remove them? I know it would vary on a trailer by trailer basis, but is there one out there that's like this and could be used in a 5x10 build?
Thanks everyone!
Harbor Freight and redtrailer have plenty of 4x8, and I even saw a 5x8 one on Harbor Freight's website. Can you take that and just extend the teardrop frame a foot on each side, front and back?
I know that 5x10 is a common teardrop size, and probably what we'd be looking to build so we could fit a queen sized mattress in there (my husband and I are NOT small people!)
Also, I see plenty of trailers for sale with mesh bottoms and side railings. Is it possible to get one of these and either a) assemble it without the mesh and the sides, or b) buy one already built and remove them? I know it would vary on a trailer by trailer basis, but is there one out there that's like this and could be used in a 5x10 build?
Thanks everyone!