Truck bed rubber mat

Tractor Supply or about any truck accessory shop. Amazon as well.

About $100+/- for a made to fit bed mat is about the cost. DeeZee, Westin, just to name a couple. Mines a Duraliner but not sure they still make simple mats.
Some of the ebay/amazon vendors ship free

I was thinking a generic cut to fitt would be a lot less.

Stall mats may be a little cheaper and thicker. They come in 4 x 6, so you'd need two to fully cover the bed.

I have a 3/4" stall mat now. I wanted to get something less stiff based on NL recommendation.

Unless you need the lift of more plywood, drop the camper on the stall mats and call it good. I do t see what you gain by going to a bed mat.

There are 2 goals here. The stall mat is slippery and doesn't create a flat support (the edges sag to the bed ridges/valleys). Second, the stall mat is 3/4" thick and NL recommends 1-3/8" for my truck/TC combo. The last extra goal is to support the camper aft of the bed by having the plywood extend beyond by 6-8".

Either way, I was simply asking for a recomendation for sourcing the mat material I've seen others use in photos.

I've not been able to find the typical 3/8" pickup bed mat in longer than 8'. If you get a fitted one it will be wider than 4', at least in front and back of the wheel wells. I've not been able to find stall matting less than 3/4". Tractor supply lists 1/2" but not in my area, and no 3/8". I have looked.

I ended up using a fitted mat, cut the pieces off wider that 4' ahead of the wheel wells (as the camper does not touch there) and used them to fill in 6" at the front, shifting the mat back. There is a little customization required. You can also buy the tailgate mat, which gives you another 5' x 2' or so of material to play with.

I can get 1/4" stall mat locally (I actually have a good amount already left over from another project), but I'm not sure it's soft enough. To me, it feels the same as the 3/4" material I already use.

I do not remember where I got my bed mat, it has been a while back, but I think it was at an Advance Auto parts store or maybe at Tractor Supply. I did have to trim it to fit the bed wheel wells.