Make your own! It's easier said than done, but it saves money. You can buy a recumbent trike for $2000 or so, then build some kind of shell out of coroplast, zotefoam, fiberglass, carbon fiber and kevlar, fabric, whatever. If you just want weather protection and not speed, the easiest and cheapest option is probably a Wizwheelz Terratrike ($1000 for a 3-speed) with a Velokit (another $1000). Look here:
velokit.com
wizwheelz.com
Finding a used trike that the Velokit would fit could save a lot of money off that $2000.
I bought an $1800 Catrike Trail, and I'm putting the finishing touches on a fabric and fiberglass-pole shell. (Just in time for summer--good timing on my part.) It's basically a dome tent on a trike, but it's not a dome, and it's a head-out design. I bought a cheap dome tent and a used tent for $35, plus a few more dollars for PVC and velcro. Then I did a lot of sewing. Someday I'll upgrade to zotefoam or fiberglass to get an aerodynamic advantage as well as weather protection. If you build it yourself, there are lots of options. Just use Google.