I already have OEM bars and yet had to get these ones because I could not trust the OEM ones with rooftop cargo box weight. Not a perfect fit but seems to work.

Amazon.com: CargoLoc 2-Piece 52" Aluminum Roof Top Cross Bar Set – Fits Maximum 46” Span Across Existing Raised Side Rails with Gap – Features Keyed Locking Mechanism, Silver : Automotive

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Check out these ones too:

Amazon.com: 260lb Loading Weight Heavy Duty Roof Rack CrossBars Replacement for 2013-2018 Toyota RAV4,Anti-Corrosion,Aluminum Black Matte with Anti-Theft Locks (ONLY FIT Original Side Rail) Sold as 1 Pair : Automotive

Shop Amazon for 260lb Loading Weight Heavy Duty Roof Rack CrossBars Replacement for 2013-2018 Toyota RAV4,Anti-Corrosion,Aluminum Black Matte with Anti-Theft Locks (ONLY FIT Original Side Rail) Sold as 1 Pair and find millions of items, delivered faster than ever.

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You could always use two 2x4's across the roof rails, drill holes for the width of the rails to accept plastic tiewraps and then secure them to the roof rails.

 

I put on a set of Malone bars. Work great with my old Yakima roof box. Most aftermarket bars fasten over top of the rails so they are wider than the OEM style which kind of fit between the rails for a sleeker look.

https://www.etrailer.com/p-MPG215.html?hhyear=2017&hhmake=Toyota&hhmodel=RAV4

 

I greatly appreciate everyone taking the time to share your considerable experience.
For this home-move, to save lots of money, I went with two pressure-treated two-by-fours, cut to 70-inces, which is inside the Rav4.4 wheelbase, to give myself some extra room to safely tie the mattress sets down. I affixed the wooden crossbars using 1/4”MLPS rope, using four passes of rope at each of the four attachment locations, which in my case are fully forward and rearward on each rail.

I did follow the much-appreciated link provided to the Autekcomma Roof Racks, as I surmise all of us that read that posted reply, and I think that is the way I will go when I purchase non-manufacture it yourself out of 2x4 roof racks.

I could not however discover a link to the Autekcomma manufacturer website. The manufacturer link simply got buried by the bought and paid for advertisement in my search engine, DuckDuckGo.