Try your LBS. I know mine always have more than a few lying around to test out. As suggested earlier though, try to "flip up" your current stem to get that positive rise if you haven't already done so. Otherwise there are typically 6, 10, and 17 degree stems that in the "up" position, will give you a more upright riding position. Given your upcoming condition, your LBS would probably be invaluable in providing advice on stem length also.