This is apparently more problematic than I originally thought. My door dimensions are 76" H x 58" W, which is not a common size.
I contacted the contractor of our house (it was an extensive remodel, not entirely new construction) who told me the doors were purchased from a local surplus store 4 years ago. I went to the surplus store and they no longer have any doors that size, nor can they order them. They say it's a custom size (which almost everyone says) but that makes no sense to me because the contractor could've chosen any size doors for this space, so I don't see why they would opt for a more expensive custom size vs. a less expensive standard size. Builders/contractors generally lean towards cheaper options.
I went to another surplus store that has a nearly identical wood door for a $998 which I think is a great price, but that door size is 80" x 60".
I also went to Lowe's who is going to send someone to my house to check everything out, but they are predicting that I will need to get fiberglass doors at about $2,000/door, then it will be painted instead of stained wood. Probably a little better longevity going with fiberglass, but it won't look as nice IMO.
I may just buy the larger size wood door from the second surplus store and see if a carpenter can modify the door frame enough to accommodate the larger door.