Okay, due to popular demand, I have attempted to automate a relatively updated list of all IPv4 blocks listed in the @spamhaus IPv4 DROP list as well as the IPv4 prefixes in their ASN-DROP list.
https://cascadiacrow.com/spamhausblocks.txt
I am using RIPE to get the advertised prefixes for the ASNs so it's only as accurate as their lookups. My list should update automatically at 00:00 and 12:00 UTC daily. It should go without saying that I'm a random crow on the Internet and make no promises so use at your own risk, etc.
At the time of this post, there are 7886 unique prefixes between the IPv4 and ASN DROP lists.
Please let me know if it does not appear to work.
Kudos to Spamhaus for maintaining these lists for public consumption and shame on the firewall vendors for not implementing the ability to block by ASN.
Spamhaus DROP lists for those who don't already have the link: