I assume like the others, you only want new because there is a 5th wheel of the brands you mention in any price range. You just have to search for a nice used unit. If it were me I'd go on the forum for the brand and see if any are for sale there. Then check out some of the major sellers on the internet get an idea of price range then check out owners offerings. I personally would buy privately but some RV dealers give short warranties (if their worth anything?).
Like said above it's a******shoot, hirer a professional and have him do a PDI, it's worth it.