Need help finding a 28x80 Door for our inherited cats

[gregzz4]

Hopefully someone can steer me towards an inexpensive door which I can use for this Balcony Cat Door project.
I've been looking on Craigslist, used building supplies, local door manufacturers and ... problem is the size needed, and the cost of new.
An el-cheapo $100 door is hardboard which will eventually peel or rot. And most are hollow.
Fibreglass custom doors are mucho dollars.

My Mother-In-Law passed last year and the Wife decided to take in her 2 cats.
Until we can let them out into the world in our neighborhood unleashed, and when not 'walking' them, I'd like to let them out on our balcony without heating the neighborhood.
Our current door has full glass so can't be modified.
So I need a door I can cut a Pet Door into.

I need a door 28" x 80" and 1-3/8" thick. I need it to be solid wood, filled or fibreglass as it is going to be an outside door.

Can any of you steer me towards anyone you know to help us out?

Thanks all