Not really difficult, colocation is available in the same buildings as the largest IX points... Places like One Wilshire, 350 E. Cermak, NAP of the Americas, 60 Hudson, etc. It definitely has a premium price.
If you can extend your horizon of view out to buildings that are in the same metro area but less than 10, 15 or 20 km of (OTDR measured) fiber from the IX point, the performance is very nearly the same, and there's a lot more options. One example would be the datacenters in Tukwila, WA and their relationship to IX points in downtown Seattle.
If you can extend your horizon of view out to buildings that are in the same metro area but less than 10, 15 or 20 km of (OTDR measured) fiber from the IX point, the performance is very nearly the same, and there's a lot more options. One example would be the datacenters in Tukwila, WA and their relationship to IX points in downtown Seattle.