@Grey WolfWell, if the actual data appears to be near impossible to find or verify easily, faking it with an educated guess should be rather safe thing to do even in otherwise accurate historical setting where the bett is fair luck. Perhaps a fictional booking company could be used as additional level of protection against that rare, but likely inevitable reader who happens to have the actual data on hand and bitchiness to pull it out.
However... if I read the implied context right and we're talking about a do-over or time travel, the accurate sporting event results, and likely the odds issued as well are on a level of complexity and volatility I would consider involving true randomness and not likely reliable, especially long term. Since you're saying you're drifting away from that as easy income source anyway, consider the imperfect -- changed -- odds as subtle hint of timeline splitting. Of course, the problem then can be the supposedly prescient bettor's inability to recall the precise odds for comparison, but apparently he does win the bett anyway even if the actuall odds may not seem quite right to him at first.
Edit: I mean, something like:
"I went to booking to make the bett, but stumbled a bit seeing the odds. I didn't recognize the actual numbers even though the order was right. I tried, but couldn't recall those either, so maybe it was just my memory playing tricks. Or maybe, are things like that starting to change already?"