I highly recommend you enlarge your plans to have enough space for a 36" fridge!! You can see the difficulty you're having finding an appliance to fit your space. Very limiting. The ability to fit a more commonly available 36" unit will reduce headaches in the future when the fridge you buy for a smaller space goes caput.

FWIW, the number of cfs don't necessarily correspond to the number of inches uniformly in the fridge world. Each manufacturer is a little different so don't focus on searching for fridges in a certain capacity.

I'm sure you've already been there, but JIC check out ajmadison dot com. The site has a great search feature to help sort by size or capacity or type, etc. You should also post over in the Appliances forum. I can't get the link from the ipad without losing my post here so look at the top of the page where it lists other forums. Appliances should be listed as a clickable link.

Some refrigs require only an 1/8" for side clearance but need 1 " space up top for heat to escape. Check and see the clearance the door needs when it opens. Some open with very little side clearance and others need a little more. If your wall sticks out past door on hinge side the refrig may open with very little clearance but remember it will only open 90 degrees. You can google the model # and brand of fridge and get specs on most all of them. It will tell you the side clearance needed when door is open. This only matters if your fridge is butting a wall on hinge side. A countertop on hinge side usually doesn't matter because fridge is generally deeper than cabinets and won't be obstructed when opening door.
Hope this helps

Check the installation guides online... Many fridges nowadays have very specific "built-in look cut-out dimensions" listed in their installation specs. They know that a lot of folks are recessing them into walls or adding cover panels, so they give you minimum space requirements. Like this:

By the way, if you are still searching for a refrigerator and haven't checked out the AJ Madison website, give it a look. It has an intuitive filter and sort mechanism. Just for the heck of it, I filtered quick on width between 30"-35", and sorted by width (narrower first) in the attached link. Obviously you can adjust other filters for other features that you value.

Here is a link that might be useful: AJ Madison website pre-filtered

Thanks everyone. I had the appliance store send their installer up and he confirmed the whirlpool fridge I want will fit perfectly (phew). We have an 18cf now, which is planty large enough for our family and small kitchen. The kitchen designer INSISTED it put in a 21cf one. We put milk, eggs, meat and produce in our fridge. Sometimes we have small containers of leftovers. I don't freeze much so there is just ice and bagels in my freezer. I suspect we are weirdos for not packing our fridge full of processed food and soda. Maybe I'll use the bottom shelf to store white wine. Hmmmm.

in truth, the size of frig should be exactly what you have determined you need on a day to day basis. A larger frig costs more to run, and a lot of empty space inside is to be avoided. I'm just wondering why the pressure to get bigger if you didn't need it? We got a new 18 sq foot-because of the freezer drawer the whole thing is a better use of space, and we still have some unused areas on shelves.

Also consider that if your kids are young, as they grow they will eat more and you'll need more frig space. Often, the need for more space is dictated by fresh produce. Some apples, lettuce, etc.

I don't know what your resale thoughts are but most others would be looking for more than 21 c.f. for a family. One teenager will push that right over.

Are you keeping the cabinets and just getting new appliances?