A different approach, which may work for you, is to install the fonts necessary as system fonts on the dyno that your app runs on.
In short: Make relevant symlinks from each font file into ~/.fonts/ upon application start.
Then, collect the TTFs you need in, say, your applications's vendor/fonts folder, version-controlled and neat.
If you were to use Ruby on Rails, you may do exactly like the following, but it's probably very doable in your Node.js environment, too.
This Rails-oriented blog post details the thing but here is the relevant code as an initializer, that you could call config/initializers/system_fonts.rb:
if Rails.env.production?
font_dir = File.join(Dir.home, ".fonts")
Dir.mkdir(font_dir) unless Dir.exists?(font_dir)
Dir.glob(Rails.root.join("vendor", "fonts", "*")).each do |font|
target = File.join(font_dir, File.basename(font))
File.symlink(font, target) unless File.exists?(target)
end
end