If you have money burning a hole in your pocket, Gigabyte has a couple CPU / mobo combos that might be of interest to you.
It turns out that Gigabyte is actually selling two bundles. We were originally told $1,599 was the retail price for the 5.1 GHz bundle, but, as spotted by Computerbase.de, a motherboard/CPU combo with a Core i9-9900K overclocked to 5.1 GHz is available for ~$2,000.