‘libfortran3’ from NASA’s OCSSW software “works for me”. The NASA software is distributed as git bundles, but libgfortran.so.3 was added to the git repository after the bundle was created, so you need to download and extract the bundle and then
git pull to get libgfortran.so.3:
$ cd /tmp
$ wget https://oceandata.sci.gsfc.nasa.gov/ocssw/opt-linux_64.bundle
--2020-05-22 09:10:18-- https://oceandata.sci.gsfc.nasa.gov/ocssw/opt-linux_64.bundle
Resolving oceandata.sci.gsfc.nasa.gov (oceandata.sci.gsfc.nasa.gov)... 169.154.128.84, 2001:4d0:2418:128::84
Connecting to oceandata.sci.gsfc.nasa.gov (oceandata.sci.gsfc.nasa.gov)|169.154.128.84|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 146899322 (140M) [application/octet-stream]
Saving to: ‘opt-linux_64.bundle’
opt-linux_64.bundle 100%[=================================================>] 140.09M 10.2MB/s in 13s
2020-05-22 09:10:31 (10.7 MB/s) - ‘opt-linux_64.bundle’ saved [146899322/146899322]
$ file opt-linux_64.bundle
opt-linux_64.bundle: Git bundle
$ git clone -b v7.5 opt-linux_64.bundle
Cloning into 'opt-linux_64'...
Receiving objects: 100% (1786/1786), 140.09 MiB | 30.37 MiB/s, done.
Resolving deltas: 100% (846/846), done.
Updating files: 100% (668/668), done.
$ cd opt-linux_64/
$ git remote set-url origin https://oceandata.sci.gsfc.nasa.gov/ocssw/opt-linux_64.git
fossa@gwlaptop:/tmp/opt-linux_64$ git pull
From https://oceandata.sci.gsfc.nasa.gov/ocssw/opt-linux_64
5b2529c..a4024af v7.5 -> origin/v7.5
5b2529c..a4024af master -> origin/master
Updating 5b2529c..a4024af
Fast-forward
lib/libgfortran.so.3 | Bin 0 -> 988064 bytes
liboc.so => lib/liboc.so | Bin
lib/libstdc++.so.6 | Bin 0 -> 989840 bytes
{oc => lib/oc}/libcore.so | Bin
4 files changed, 0 insertions(+), 0 deletions(-)
create mode 100755 lib/libgfortran.so.3
rename liboc.so => lib/liboc.so (100%)
create mode 100755 lib/libstdc++.so.6
rename {oc => lib/oc}/libcore.so (100%)
$ sudo cp -p lib/libgfortran.so.3 /usr/lib