Radical Spencerians like Auberon Herbert and Wordworth Donisthorpe represent an interesting bridge between the capitalist and socialist wings of libertarianism, palling around with the Liberty and Property Defence League on the one hand and Benjamin Tucker on the other (and being hailed by the latter as fellow anarchists evidently the benighted Tucker had never had a chance to read the AFAQ).
I see that Google Books now offers some previously hard-to-find works by Herbert and Donisthorpe. One is Herberts A Politician In Trouble About His Soul (1884), a presentation of political philosophy in dialogue form. The quasi-anarchistic last chapter is widely reprinted as a separate article under the title A Politician In Sight of Haven, but the full work has not previously been available online.
There are also four books by Donisthorpe: Principles of Plutology (1876), Individualism: A System of Politics (1889), Law in a Free State (1895), and Down the Stream of Civilization (1898). Of these the second and third have been available online for a while, but the first and the fourth have not.
Down the Stream is a memoir of Donisthorpes travels in the Mediterranean; his sometimes bigoted opinions can make it annoying (anomalously for a radical Spencerian and an anarchist, he was an apologist for British imperialism), but it is also witty and enjoyable, and makes a nice pairing with Richard Harding Daviss somewhat similar Rulers of the Mediterranean (1894), also newly available on Google Books. Rothbard speaks highly of Plutology in his History of Economic Thought. Left-libertarians will be especially interested in Donisthorpes theories of labour capitalisation in chapters 6 and 7 of Individualism and chapter 8 of Law in a Free State.