Gas water heater question

[Tanya F.]

Not sure if this is something I want to do myself, but maybe some here have come across this issue before.

Our chimney is in bad shape.  Rather than repair it we are considering doing what we did at our other property, taking it down.  The history:

Both (2 family) properties were originally built with chimneys venting two gas water heaters and two furnaces. We've upgraded all the furnaces to direct vent, so the story begins with the chimneys venting only two water heaters.

At property 1, the two gas water heaters didn't need replacement but we opted to replace them with direct vent models anyway, so we could take down the chimney. Two new water heaters turned out to be much less expensive than repairing the chimney.  We didn't bother with careful roof patching because the following year we replaced the roof.  This was all a while ago.

Now back to the present at property 2.

We cleaned the gutters yesterday and got a good look at the chimney while we were up there. It's flaking all over the place.   Currently venting only two water heaters. My question is, does anyone know of a conversion kit to change the existing venting for gas water heaters? These two water heaters are relatively new (as opposed to the ones in property 1- which were getting old). The roof is less than 10 years old.  We'd like to take down the chimney and patch.

I tried searching for water heater vent conversion kit and didn't find what I was hoping to find. Perhaps someone on here has done something like this? Or might be able to direct me somewhere? I haven't called a plumber yet.