There is NO exact equivalent for HC-110. Ilford makes a developer that is similar but not the same. So there is no way to really mix the developer of one company with the replenisher of the other. Freestyle Legaacy Pro L-110 which has been mentioned in this thread and in others as a substitute but is not even close to HC-110. All you have to do is look at the two MSDS's. They really need to stop suggesting that they may be the same.

Kodak suggested a self replenishment system but never elaborated on the idea. So you are limited to using HC-110 as a one-shot or doing your own testing with self-replenishment.