While many of their Abs are for FC, there are a number of other sources which inidicate IHC applicability. Our listings may be a good place to start. For example: https://www.linscottsdirectory.com/antibodies?q=CD45RO
Filter for IHC Applications, and follow "more info" to supplier's data pages.
You may also want to look through the review sites pabmabs.com and antybuddy.com