A car spring from a small car or boat trailer would be thin, and make a nice bark peeler. What about a "Frow" type tool ?? That's what is used to make riven shingles.
In case you aren't aware, they are an "L" shaped device. A car spring, cut about 15" long, if it already has a loop-eye on the end, and make a wooden handle to drive into the loop-eye. Then, just tap the blade under the bark and bang it on the "Free " side, while pulling on the handle side.
It would-should work just fine and not be tough to use, as a drawknife might be. Just don't sharpen it like a knife. Make it more like a chisel, and back grind the edge just a tad, so it won't dig into the wood near so bad as a knife edge would.