Try a z200, Z250 or KH125 ducktail. Heres one (
http://auction.netbikes.com.au/item.php?id=5013 ) Fabricate a small seatpan from either sheetmetal or alluminium to bridge the gap between the tank and the ducktail. Add foam and a bit of vinyl and it could be done for under $60.
I have a seat here which has rooted viinyl and foam but remarkably the seatpan is immaculate and I am reluctant to let it go because of its condition.
Try also Motumbi somewhere on the north coast of NSW
http://www.classic-motorcycle-fiberglass.com/index.html You can get a fibreglass unit and upholster it to suit.
On the LH switchgear, yes I realise I do have one - still to be confirmed though - its in the back shed and may take a while to get to but I'm pretty sure there is one down there. Everytime I go down there though I get sidetracked as I find something else I have been looking for and get all excited and forget why I was there in the first place!
Try here for parts also.
http://shop.wemoto.com/index.dyn . For some reason alot of NOS has ended up in Thailand and with the 100's and 125's being popular in asia and the UK make sure you always search "worldwide" or visit the country's specific AUCTION SITE.
Note however that there is nothing and I mean it there is nothing that is shared between a KH125 and a KH100. They were both completely different designs. The 125 was not the same bike with a larger bore. Just like the the ER6 is not the same as a Z750. know what I mean?
Having said that though some similarities exist between the 100 and the AR80 - not many though and parts for those are just as hard to find. But are worth a look.