whats wrong with your current bars? you may be able to clean them pretty good. I think that possibly Dave Miller, or someone did repop some for the Bonanza's in the past or just have yours rechromed if you are going for a restoration (at least save your bars if should you decide to do that at a later date)
If thats not your thing, Might try the EMGO catalog and and see if there is something that comes in close they usually have measurements in the catalog. If you do find something that you like in the emgo catalog, take the parts number and search on ebay and amazon. Last time I bought bars I did it that way and got them really cheap, as everyone in the MC world carries emgo parts like everyone in the mini bike/kart world carries the Azusa line. If they don't have knurling, in your case that's probably what you want to look for because not much these days are going to be a match, you can take like a center punch and go around the bars and make some divots or scribe some marks giving the riser something to grab.
And yes, your engine is a transplant. its about 30 years newer than you bike is.