There's one on eBay for £99

Make an offer or ring round the breakers for a better price.

hi guys, looking for a fellow biker, he lives in the UK and cant find this part anywhere, the product code is 64501MGJD00, it looks like part of the front cowling, we have run out of ideas for tracking one down, he even phoned Honda japan. no luck.

I changed my chain and sprockets a about a year ago on my SC58 at 20900 miles. From measurements I estimated it would easily last to around 24000 miles however, as I was going on a 4 day trip I decided to edge on the safe side. I took the swinging arm off at the same time to check and grease the bearings, all was ok but there was not much sign of grease. After taking advice from a local motorcycle repair mechanic/ parts supplier I purchased a CZ 530 DZX chain and RK sprockets from him, he joined the chain for me (saved me buying joining equipment) and I then completed the fitting. The cost was just under £100 all in which I think is good value for a complete new drive system. The original drive sprocket had no sign of any grease on the splines so there was plenty of the red dust, I used molybdenum dark grey grease fitting the new one. The old sprockets showed very little signs of wear.
As Art points out the most important point is the joining of the new chain, its only as good as the weakest link, and getting it done professionally meant it was done properly with good quality tools. It depends on your time and ability but to me it makes good sense to take the swinging arm off for a bearing check/re-grease at the same time as changing the chain and sprockets.

I've heard tell of marking the gearshift arm against the gearshift spindle before and I'm not sure why this would be necessary. There are two indent marks, one on the arm and one one the spindle, just note how they line up before removal.

Before you remove the gear shift arm from the spindle , make a mark on each ( felt pen dot works) so that they line up correctly when the arm goes back on.