I used the two lists [0] from google to build a list. You don't want their public cloud IPs so it seems you'll need to subtract public cloud IPs from their total IP list. I used the program net-consolidator to do the subtracting. I don't know how good the python program is. This is my first time using it.
[0] https://support.google.com/a/answer/10026322
Reference : https://developers.google.com/apps-script/reference/url-fetch/url-fetch-app
Commands:
curl -s https://www.gstatic.com/ipranges/goog.txt > full
curl -s https://www.gstatic.com/ipranges/cloud.json > subtract.json
jq '.prefixes[].ipv4Prefix' subtract.json > subtract.quote
cat subtract.quote | sed 's/"//g' |grep -v nul > subtract
git clone https://github.com/TKCERT/net-consolidator
python3 net-consolidator/net-consolidator.py -f full -s subtract
Which gave me this list. I didn't actually verify the accuracy of this generated list.
8.8.4.0/24
8.8.8.0/24
8.35.200.0/21
34.64.0.0/18
34.96.0.0/18
34.98.0.0/18
34.98.136.0/21
34.98.144.0/20
34.98.160.0/19
34.98.192.0/18
34.99.0.0/16
34.100.0.0/17
34.101.0.0/20
34.101.16.0/23
34.101.19.0/24
34.101.28.0/22
34.101.32.0/19
34.103.0.0/16
34.104.0.0/20
34.104.16.0/21
34.104.24.0/23
34.104.26.0/24
34.104.28.0/22
34.104.32.0/20
34.104.48.0/24
34.104.53.0/24
34.104.54.0/23
34.104.56.0/23
34.109.0.0/16
34.110.0.0/17
34.112.0.0/14
34.116.8.0/21
34.116.16.0/20
34.116.32.0/19
34.118.128.0/17
34.119.0.0/16
34.124.64.0/19
34.124.96.0/20
34.126.0.0/18
34.126.224.0/19
34.127.128.0/19
34.127.160.0/20
34.127.176.0/24
34.127.181.0/24
34.127.182.0/23
34.127.184.0/23
34.127.192.0/18
34.128.0.0/16
34.142.128.0/17
34.143.0.0/16
34.144.0.0/16
34.152.64.0/18
34.152.128.0/17
34.153.0.0/16
34.154.0.0/15
34.156.0.0/16
34.157.8.0/21
34.157.32.0/22
34.157.44.0/22
34.157.80.0/20
34.157.96.0/19
34.157.136.0/21
34.157.160.0/22
34.157.172.0/22
34.157.208.0/20
34.157.224.0/19
34.158.0.0/16
34.160.0.0/13
34.174.0.0/15
34.177.0.0/16
34.178.0.0/15
34.180.0.0/14
34.184.0.0/13
35.187.128.0/20
35.190.96.0/20
35.190.240.0/20
35.191.0.0/16
35.199.128.0/20
35.201.32.0/21
35.201.40.0/24
35.201.42.0/23
35.201.44.0/22
35.201.48.0/20
35.203.192.0/20
35.203.208.0/23
35.203.220.0/22
35.203.224.0/21
35.203.240.0/20
35.206.0.0/19
35.218.0.0/16
35.219.192.0/18
35.220.28.0/23
35.220.30.0/24
35.229.0.0/20
35.230.192.0/19
35.230.224.0/20
35.235.128.0/18
35.235.192.0/20
35.235.208.0/21
35.235.224.0/19
35.242.28.0/23
35.242.30.0/24
35.243.16.0/20
35.243.48.0/21
64.15.112.0/20
64.233.160.0/19
66.102.0.0/20
66.249.64.0/19
70.32.128.0/19
72.14.192.0/18
74.114.24.0/21
74.125.0.0/16
104.154.0.0/20
104.154.112.0/24
104.154.122.0/23
104.154.124.0/22
104.155.240.0/20
104.196.64.0/24
104.196.72.0/21
104.196.80.0/20
104.199.64.0/23
104.199.240.0/23
104.237.160.0/19
107.178.192.0/20
107.178.224.0/20
108.170.192.0/18
108.177.0.0/17
130.211.0.0/22
136.112.0.0/12
142.250.0.0/15
146.148.0.0/23
172.110.32.0/21
172.217.0.0/16
172.253.0.0/16
173.194.0.0/16
192.178.0.0/15
193.186.4.0/24
199.36.154.0/23
199.36.156.0/24
199.192.112.0/23
199.192.114.0/24
199.223.237.0/24
199.223.238.0/23
207.223.160.0/20
208.65.152.0/22
208.68.108.0/22
208.81.188.0/22
208.117.224.0/19
209.85.128.0/17
216.58.192.0/19
216.73.80.0/20
216.239.32.0/19