The Dream 50 isn't hard to find.
They were made new, starting in 1997, and I think they had production until about 2005.
Limited editions.
But, they are pretty expensive, and the collectors keep the prices up.
I think they are around $4k.
You might find one cheaper if the owner put mileage on it, and it's not pristine.
If you like little bikes, a pretty cool one that can still be found somewhat reasonably priced, is the Sears 106SS. 98cc 4-stroke.
It was imported during the 1960s by Sears, and it was made by Gilera in Italy.
Gilera bikes are famous for being GP champions in the 1950s, and most Gileras are super exotic and ultra-high priced. The were similar to MV Agusta of the time period, and even had similar engine designs.
The Sears 106SS or 124SS, are true Gilera bikes, with a Sears name on the tank.
You can sometimes find them for a couple hundred bucks, in need of work.
Parts are not available, but there are alot of enthusiasts who have an active parts network, and there are even some people producing some new stuff for them.
Here's a photo of a Sears-imported Gilera 106SS in stock form
This bike is an original Gilera 125 GP racer. You can get all this bodywork, including the dustbin fairing, from Air Tech, and turn your Sears 106SS into something that looks like this.
They are the same frames and engines(basically), so it will appear to be just like the old GP racer. You could do this with about $2k invested, if you get a cheap 106SS to start with.
The same kind of thing is true with Benelli.
Montgomery Wards imported single cylinder Benellis all thru the 1960s.
They are genuine Benelli bikes, with the Montgomery Wards or Riverside logo on them.
Here's a Montgomery Wards Riverside 250cc 4-stroke by Benelli
They even made a 360cc desert sled called the 360 Mojave, which is like a little Rickman type Benelli.