Bob-
I've got Airkewld brakes on my bus, and I've dealt with Pete. What you want is not a specialty part-- it's just specialty hardware, and you can get that from McMaster Carr or Fastenal. If Pete had it, he'd most likely be buying it from McMaster Carr or Fastenal.
Art's link is actually a fantastic deal-- it's $13 or so for a pack of 100. I'd pay attention to the head size, you want a reasonably big head to get a good bite on the spacer.
McMaster Carr has everything you need. They have the bolts in any length you might need. I got the part numbers for the bolts, the countersink, the whole shooting match last fall. You can buy in quantities of 5 for $12.14. The P/N for the M14 (2.0) x 40 is 91294A414. The link is here (Link to 14 mm Flathead Screws) I don't think 40 mm is going to be long enough for you to use your spacers, but thats OK-- they've got longer ones as well. They ship from Chicago, and will be here in the AM if you order before 7 PM or so.
Fastenal has a branch in every town with more than 35 people in America, but none of them stock anything. Fastenal will be slower and cost more than McMaster Carr.
The whole thing would take an afternoon, and you'd be ready for drumskins (which I'd buy from CB for $100- Here is the Link to the Drumskins). The painted (non-chrome) wheels are the hard part-- fopr some reason, they only come in about once a year from China. CIP had them last fall, and still lists them on the website for $50/. (The Link to the Wheels is Here). I'd get a set before they are NLA for another 6 months.
50 bucks would take you all the way with McMaster Carr, tool and freight and a trip to Perdue's included. A Benjamin gets you the drumskins, 2 more get you the wheels. You can countersink your adapters on my drill press so the labor is free. That's as far as I can take you, my friend-- this is by far, the least expensive way to get to wide 5s there is out there.