How to use an ActiveRecord plugin in a non-Rails project

I’m using ActiveRecord on a Sinatra app. I need one of my tables to be
sorted, so I’m using acts_as_list
(GitHub - brendon/acts_as_list: An ActiveRecord plugin for managing lists.).
However, it isn’t a gem, so I don’t know how to get it to work with

Currently, I just cloned the source into a dir named “vendor”. This
but when I search my code, it keeps including acts_as_list code in the
results. It also means more folders and files, so just generally more
overhead. I’d like it to be as transparent as all the gems I use.

Is there some way to get Bundler to deal with it, or is there a best
practice for this situation?

(I was thinking I could probably fork it, give it a gemspec, and then
Bundler to look at my forked repo, does that sound reasonable?)