I check RVTrader regularly, molded FG trailers rarely show up, maybe 2-5 nationally at any time.
In this trailer size, particularly molded, you will not find both permanent bed and four-seat dinette. The "double" bed will always also serve as dinette, and if there is a second dinette, it will be two seats. The bed will hardly ever be a queen, and is usually even smaller than a double, because the narrow width of these trailers makes the bed necessarily short.
The type of layout you want, with single bed or bunks, will usually put that bed up front. In a Casita, that means a 'standard' model, i.e. no bathroom. Casita has not sold many in this configuration, most buyers are looking for a bathroom. Scamp has probably sold more in this configuration (they will be 16-foot) over the years, and in the Scamp it is possible to find the bunk up front and a bathroom in a small closet on the street side.
You can also find the single front bunk in 13-foot models, many different brands, but then there is no room for a side dinette. These may or may not have a small closet holding a bathroom or at least a porti-potti space.
16-17 footers with a side dinette, that dinette can be made up as a bed. Because there have been options for a bunk over the front bunk, and a bunk over the dinette, there have been 16-foot egg trailers sold that can sleep six people. Probably not very many, hard to say though, because assorted manufacturers been building these for at least 50 years, and 40-50 years ago sleeping space was more important to buyers than it is today, so they sacrificed other facilities to provide for more bunks.
To help your search, the Casita model with the side dinette is called Spirit. "Standard" means there is a seat/bunk up front, "Deluxe" puts a bathroom up there as standard equipment.
Scamp, it is more complicated. Standard vs Deluxe are more like trim levels, and what might work could be Standard 3 or 4 with from seat without or with closet bathroom, or Standard 6 or 7 with side dinette. Standard 6 is laid out like a Casita Spirit Deluxe, Standard 7 like a Casita Spirit 7.
Scamp 16 Deluxe A has closet bath at the side and a two-seat dinette/single bed up front, Scamp Deluxe B has bigger bath up front, side dinette/single bed (again like Casita Spirit Deluxe).
Scamp has had other variations on these configurations over the years. Casita, being much newer, has pretty much made in the past what they are offering new currently.
Oliver 18-footer (now building as Legacy Elite) has a floorplan like Casita 16-17 Spirit Deluxe. Construction and fittings are more upscale, so thus is the price higher.
Unfortunately for shopping used, advertisers seldom give this model information, so you need to look at pictures if online, or get someone to describe it if you are calling.
I've not researched much the other manufacturers, there have been many in the past. Most of the older egg trailers, however, were the 12-13 foot models, which can be made to work for a single or couple, can be more of a problem if you need room inside for a 3rd or 4th person, even a small child.
I've visited Casita, I am impressed with how they are made. I've looked into Oliver, which I think also very well made, has been offered in different sizes over the years, but total production has been small, making used hard to find.
Bigfoot makes some excellent all-season molded fiberglass trailers, sold them through dealers, mostly in the Northwest. But Bigfoots might be kind of heavy for a Ridgeline tow.
Because most of these molded trailers were sold factory direct, made to order in the later years, what you find will depend on where you shop: Scamp in Great Lakes region and upper Midwest, Casita in southern Plains and parts of the South, Escape and Bigfoot along the Pacific Coast, and Oliver in the Mid-South.
Many other brands come and gone, but still out there, because this type of TT often holds up fairly well in long storage.
The collection of features you want is usually found in full width travel trailers with at least 17-foot box, for 19-20 overall length. In some box trailers at least 7-foot wide, 18-19 long, you might find a double bed in one end, which could have a single bunk over it, and a small dinette in the other. These usually have 16 or 17 in the model number, approximate reference to the box size rather than overall length. Bigfoot's 2500-175FB is one example you might find used on the West Coast. It is molded fiberglass, but unlike the traditional egg trailers, it is more like a box trailer, full-size RV width and height, and in this case the model number refers to overall length rather than box length.
