Does anybody have any good sources for parts our bikes stateside besides Partzilla, Partsfish, and Stadium Yamaha?  They all seem to be pulling from the same part inventories; that is, they all have the same parts list that are available and unavailable.  I'm looking for the rear rubber grommet that the oil tank fits into under the seat, a taillight screw (one of the long ones that holds on the lens) possibly a headlight, and a horn, but no one has them.  Its for a CT1B.  Ebay doesn't have much there either.  It's a little frustrating but the reality is that these bikes are old and getting older.

Try Speed and Sport they often have parts others don't. 

Here's your oil tank grommet

Your lamp screw

Horn, yeah that's going to be tougher to find NOS. There are some non-OE looking alternatives on eBay, I would broaden a search to look for any 6V CT/DT series horn, and just pick & search to find one. You may have to restore it depending on the level of shine you're looking for on your CT1. 

Thank you!  I'm a little nervous about Ebay, we've had credit cards hacked twice after using it, but I closed our account and will open a new one to make sure it doesn't happen again.  My horn makes a slight noise, like it's dying.   Has anyone ever tried to restore their horn?

If there is an adjuster screw on it, then try moving this into a position, in or out, where there is an improvement.

If still no good, then you can have a go at fixing it if it isn't pressed together. I have posted a couple of times about fixing them - here's a link to one of the posts.

If your horn is held together by rivets, then these can be drilled out and replaced by screws/bolts and nuts. Just make sure that you take photos as you go, so that you know how to re-assemble the horn!

Regarding searching for parts, look on the CMSNL website, and the internet in general, to research what a part you need actually looks like - plenty of misdescribed listings out there. Then use very general terms when searching (eg Yamaha speedo, Yamaha indicator) and see if any image matches what you need (ignore what the seller says it fits!). 

Yamaha RD125/200 horn repair - Vintage Enduro Discussions (yamaha-enduros.com)

Searching Ebay with a yamaha part number will eventually get you the correct part.

I agree, but be wary of parts that have been taken out and put back in the wrong box! 

I picked up a ridiculously cheap new RD250/350 tacho, due to it being listed as one for a XS500, as that was the part number on the side of the box. Fortunately I knew what I was after looked like and so took advantage of this.