It may take longer and be more work, but anything thick that needs bent can always be cut and welded. Make sure that you account for where all your rock is going to go and make it as easy as possible for clean up. I would suggest building your own barrel, eaither find some pipe, or something to repurpose, like an old propane tank (just don't blow it up cutting into it). Once you have it the size you want just cut out sections where you want your screens to be, then just weld your screens over the holes, punch plate would be best. Then in the scrubber section weld in a couple agitators and your good to go. As far as a direct chain driven barrel, as stated above the sprocket will be very expensive. You might have better luck finding someone with a CNC plasma cutter than can cut you one out of a sheet of steel. The right person would do it cheaper than you can buy one and hopefully you could get the steel from somewhere cheap, possibly used. Or you could scrounge around to try to find one used off of something like an old cement mixer. Many parts are expensive new, but with some searching and a little extra work, you can turn old scrap into your new trommel for pretty cheap.
