I suspect you've found a trailer by now but I'll share my experience. Last year, I posed a similar question. with a similar story for transporting my Freewheeler. Cost and space were my biggest challenges. A big box trailer would serve a lot of wants, but no convenient place to keep it. Online I found a person within 100mi. who builds trailers as a side hustle. I drove out and looked at a couple of samples of his work and discussed my specific needs. He had ideas and knowledge that I didn't and I ended up having him build me a trailer that exceeded my plans for considerably less money than I expected to pay. The trailer is a 6',X10' flat deck with a full width ramp tailgate and a 4" dropped 3klb axle. I park it in my garage and drive my trike directly on and off after every outing. As mentioned before, it makes safety checks and servicing much easier. FWIW - I am very happy with my trailer and I couldn't have done better within my price range. There is risk and wait time when creating a "homemade" trailer but with some diligence and luck, you can have the best trailer for you.