Ironic phrase like Russian’s “no, didn’t hear”

Here’s a bit of dialogue which I literally translated from Russian:

― You should get a girlfriend!

― Girlfriend? Didn’t hear. . . .

The idea of the answer is to self-ironically point out not only that the guy doesn’t have a girlfriend, but also that he hasn’t even heard of their existence.

In Russian, it is a kind of idiom. What is the right way to express a similar idea in English?

Another idiomatic option (at least in British English) would be:

You should get yourself a girlfriend.

Sorry, never heard of it.

The use of the impersonal pronoun "it" is part of the humour; it indicates that the speaker not only has no girlfriend, but doesn't even understand the concept that a "girlfriend" might be a type of human being.

A corresponding conversation in English might go something like this:

― You should get yourself a girlfriend!

― A girlfriend? What’s that?!

It’s more sarcasm than irony, and the reply is often “deadpanned”.

If you want to turn the sarcasm back on the person giving obvious advice, you could say something like

A girlfriend? I didn't get the memo.

or

A girlfriend? I must have missed a meeting!

or

A girlfriend? Gee, why didn't I think of that?

Any of these implies that the advice is so obvious that the person giving it is either stupid or callous (or both) for bringing up a topic that is already causing you significant discomfort.