You are correct on the centre stand. You need a bracket to hold it down.
If your caliper is not leaking, just take it apart and reuse the existing seal. Clean and polish everything, paying very close attention the the seal groove. Make a small, bent pick and scrape out all the crap in the seal groove. I also use a small brass brush wheel on my Dremel, and polish that groove spotless. If the piston is badly corroded, replace it. Have you tried your local Honda dealer for parts?