Mark,
Start looking at scrapyards, old farmer fields, etc. I bet you could find a truck being scrapped/parted out close to home and you could cut out a seat riser in about 20 minutes with a spot welder cutter and a drill. Then plug weld it into your truck. No fabrication required, it will fit perfectly, and this will restore it to stock if that’s what you’re after. You might get one for free.
Heck, I’ve been given whole trucks doing this when I ask if I can buy/grab a part from trucks sitting in fields. I got a fairly complete 51 GMC 1/2 ton for a 26 oz bottle of whiskey. I took what I needed and parted the rest out for $600. I got 51 1 ton for a flat of beer. I haven’t sold anything off it yet. A 1951 Chevrolet 1/2 ton for nothing. His response, “Take it. The crusher is coming next week to clean up this mess.”
Ask around, you’d be surprised what some people will be willing to give you a bargain on. Others might try to take you to the cleaners but it’s part of the hunt! Good luck!