natbib: modifying citation style for particular source type, while others remain default

Question

I'm using natbib and would like to modify the punctuation style for one particular type of source (classical texts), while punctuation for remaining sources should remain at their default settings.

In particular, I would like to cite ancient texts without author names and without commas: e.g. Aristotle's Politics, section 123, would be referred to in-text like this:

blablabla (Politics 123)

whereas other sources should be referred to in-text in the default manner, i.e. as author-year, with a comma between year and page:

yadayayaya (Smith 1992, 33).

So far I'm using \defcitealias and \citepalias, which works fine except for the punctuation:

\defcitealias{Aristotle1992}{\textit{Politics}}  
\citepalias[123]{Aristotle1992}

results in

(Politics, 123)

=> I would like to get rid of the comma here, while still keeping the comma for the other references.

Is there any way of achieving this from within the natbib package (if at all possible, I'd rather not switch to e.g. biblatex)...? I'd be immensely grateful for any help.

---

Here's some example code (hope this classifies as a workable example):

\documentclass{article}
\begin{filecontents}{\jobname.bib}
@BOOK{Aristotle1992,
  title = {The Politics},
  publisher = {London: Penguin},
  year = {1992},
  author = {Aristotle}
    }

@BOOK{Smith2003,
  title = {Blalala},
  publisher = {London: Penguin},
  year = {2003},
  author = {Smith, John}
    }
\end{filecontents}  
\usepackage{natbib}  
\begin{document}  

\defcitealias{Aristotle1992}{\textit{Politics}}    

This is as close as I get to what I want, but I would like to get rid of the comma:  

\citepalias[123a]{Aristotle1992}  

Other sources should be referred to in the usual way though (author date, page):  

\citep[p.~222]{Smith2003}  

\bibliographystyle{chicago}    
\bibliography{\jobname}  
\end{document}

Answer 1

Put the code just after usepackage{natbib}

\usepackage{etoolbox}
\makeatletter
\let\save@NAT@cmt\NAT@cmt % saving comma 
\def\restore@NAT@cmt{\global\let\NAT@cmt\save@NAT@cmt} % restoring comma
\def\fix@NAT@cmt{\def\NAT@cmt{\space\restore@NAT@cmt}} % fix for citepalias
\preto\citepalias{\fix@NAT@cmt}{}{}  % patching citepalias
\makeatother

The output:

Answer 2

You may use the classics package too:

\documentclass{article}
\usepackage{classics}
\newclassic{Aristotle}{#1|\textit{#1}|#1}

\begin{document}

\Aristotle [Politics]{1260}[a]

\Aristotle [Politics]{1260}[a][2]

\Aristotle*[Politics]{1260}[a][2]{1261}[b][3]

\end{document}

And this is how to use classics in conjunction with biblatex, biblatex-chicago, or natbib (and deimi's answer): you need to enclose \Aristotle in braces.

\cite[{\Aristotle{1260}[a][2]}]{Aristotle1992}