Is this what you are looking for? Sorry I only have the picture. Should be able to scale something pretty accurate from it.
Flattop.

Holy moly! That's exactly what I am looking for. Thanks for the picture. Where did you find it? Lou

It was buried in the media files of a Facebook RG 500 group page. Fortunately, it was "public".
Flattop

Great find flattop!
The forum comes through again.
Paul

That looks better, now the hard work. Lou

The people on this Forum are unmatched in friendship and generosity! Received an envelope from my buddy Paul Hewitt up in Canada! He spun up a few knobs for my anti-dive valves. How thoughtful is that! What a pal! Still need to fit up, but what a great start! Thanks Paul. I added a picture of the hoses I made for the anti-dive. Waiting for some fittings. Lou

Hey guy's, in my desperate attempt to keep this post and the Forum alive, here's some more stuff I'm doing. The bell mouth on the rear carb of the Adamo bike had a broken bolt (or at least I thought it was) that holds the bell mouth to the carb body. I always wondered how they covered the 'bolt holes'. Did they fill it was some magic molten metal, was it a plug over the 'bolt'. I keep referring to bolts because when I bought bell mouths in the past they just had a countersunk hole, and I'd put in a 4mmx.70mm Allen head 14mm long if you were wondering. Never thought about filling it in, mostly cause I didn't know what to do. I called my buddy Neville, who is my mentor and knows everything, and asked him how he would approach it. He thought it was probably a plug and that I should drill it, grab hold with a screw and try and pull it out after using a heat gun to warm it up. Sounded good to me, and was able to extract the broken plug. I didn't see an Allen head. Strange. So I now went to remove the good side as I still had to get the broken threaded piece out of the carb body. I did the same procedure and found it didn't just come out. I put the screw gun in reverse and saw the plug start to back out. Eureka! It's a threaded aluminum plug. Not an Allen head bolt. In the future if I ever have to do this again, I would use a broken bolt extractor. Great, now who on the Forum has some Malossi aluminum bell mouth plugs they want to sell me! Lou

Is it possible they left the plug long then shaped it to the bell mouth after.
I would turn up a plug tap one end maybe 5 or 6mm, thread in a bolt cut off the head, thread the long plug in, once tight cut of the excess and shape to the bell mouth.good luck
Paul

Ha! that's what I was going to do! Yes I believe that's what they do. They make a plug with a thread and then shape it. I'll green loctite a bolt, into the ally plug, cut, shape, polish. It broke because it's a fragile 4mm threaded ally piece. I edited my response, Thanks Paul! Lou

I wonder how they did this every time I look at one of these. But Paul beat me to it. I think they hand-shaped the end once inside the bellmouth - when they polished them. No special part coming your way, Lou. Just more labor. MikeV

PS: The knobs on the anti-dive gismo look good Paul.