It depends on how many such patches you have.
I don't think any code for doing what you want to do exists, so you'd have to write something yourself.
If it's just a handful, what you're doing right now seems like the right approach. Anything else will almost certainly cost you a lot of time, and then you run afoul of XKCD #1205.
If you have a decent set of patches, you might be able to use some continuous integration system (say, buildbot) together with dgit to maintain your patches in git, and rebase your patch branch onto version that was newly uploaded. After having done so, your CI system then calls
dch to create a new changelog entry with a new version number, feeds it to
sbuild to build the package, and uploads it to a local repository (something like reprepro which you enable on all your hosts.
It's doable, but would be a lot of work to set up; and depending on how much time you spend maintaining your patches, might not be worth it.