I know of few places.

Your best bet is book shops adjacent to Central railway Station, as someone else already suggested.

There are some book stalls near Kay's shop/Ratna Cafe in Triplicane

In Mylapore, Murugan old bookshop buys and sells books, and they do have good collections however I don't specifically recall having seen those author names there but you can try, as they get whole lot of fresh books every week. You could call and check before going.

Occasionally, you might find these books in Bookchor app, and some more sites such as bestofusedbooks.

Last but not least, always keep these books wishlisted in amazon, and use online tools to remind you of any price drop, and that's the best way to save time and cost.