There are no easy solutions. The parts on ebay, the prices are driven by supply and demand. Instead of being on here typing, you better find the honda parts numbers you need and start calling dealers. Also prepare to dig deep. Not a cheap hobby if you want to seriously redo a trike. Best of luck. It's also not uncommon to start looking for parts in other countries. If you are not prepared to put in some time and effort, then I don't know what to tell you.
Nicholson 500x (Project)
Nicholson 185s
Nicholson 110 (That takes an atc70 tank)
Ascott 500 head/350x (Project)
Homebuilt Racer Chromoly Suspension 110 (Ragin Runt)
PK Racing Suspension 70
A+ Inc Suspension 70
AWS Aluminum 90 frame
Hi Performance ATC Suspension frame rd350
Hi Performance ATC Suspension frame 90