Which third-party portafilters and baskets do you recommend for the Flair 58?

Thanks to the industry-standard size, any 58mm basket will work on your Flair 58. 

In regards to the portafilter itself, we cannot guarantee aftermarket compatibility, but most 3rd party pieces reported to be an E-61 compatible portafilter should work on your Flair 58. Look for a portafilter with similar "wing" spacing when compared to the portafilter your Flair 58 came with.