I am currently refinishing a 60" round Nichols & Stone pedestal table that has an 18" leaf.

You could check Facebook Marketplace for high quality dining tables.

It may or may not need to be refinished. Lots of options for new dining chairs, depending on your style.

(IIRC, I paid $150 for the table.)

My sister just bought one last week. She went to about 4 local furniture stores and they all had round tables with a leaf. They did not have them in stock and the wait for most furniture is a few months. She was able to find different leg configurations, different finishes and different sizes.

If you are looking for new, you may need to order and be patient.

Check Goodwill, Habitat for Humanity, and check your local antique shops.

We refinished a round oak pedestal table that had lost its leaf, so ordered a 12” wide oak plank cut to size, finished it to match the table and drilled holes so the existing pegs would fit in, Window hardware on the underside holds table together. It is 48” in diameter as a round table, 48” x 60” as an oval. We could seat 6 -8 at the most when expanded, so to seat 10 you would need an additional 12” leaf as well. You would also need to make sure you have good support on each end. Chair size matters, too. Happy hunting.

Room and board has a couple of options though the styles are on the less modern looking side to me.

IMO this is a more traditional look so probably why you are have issues finding many.

If looking for used and wanted more modern I would be searching for the key words teak or MCM.

If looking for new I would be going to a higher end furniture store that sells more modern furniture and ask them what they have available that you can order.

https://www.ethanallen.com/en_US/shop-furniture-dining-room-tables/cooper-round-dining-table/156733.html

https://www.mortisetenon.com/products/60-round-reclaimed-wood-extension-table-with-metal-base

https://www.wayfair.com/furniture/pdp/gracie-oaks-decebal-round-extension-dining-table-w002144039.html

With a 60" round table you need a fairly sizable base to support the top, so there won't be any with truly streamline bases.

Etsy - 54" round with 2 18" leaves

https://www.etsy.com/listing/1274599063/extendable-round-table-round-dining?ga_order=most_relevant&ga_search_type=all&ga_view_type=gallery&ga_search_query=60%26quot%3B+round+table+with+leaf&ref=sc_gallery-1-2&frs=1&plkey=0011ebf942636a879b27b856b6a62e3072229362%3A1274599063

Another 54 with one leaf

https://www.etsy.com/listing/701736974/round-extendable-table-with-leaf-in-your?ga_order=most_relevant&ga_search_type=all&ga_view_type=gallery&ga_search_query=60%26quot%3B+round+table+with+leaf&ref=sc_gallery-1-1&pro=1&frs=1&sts=1&plkey=b0745f8ed7426f69da3422b6442e310b074336c7%3A701736974&variation1=2796513659

50" with two 20" leaves

https://www.etsy.com/listing/448704812/john-mortensen-teak-dining-table-with-2?ga_order=most_relevant&ga_search_type=all&ga_view_type=gallery&ga_search_query=60%26quot%3B+round+table+with+leaf&ref=sr_gallery-1-7&frs=1&organic_search_click=1

Thank you for this option, Jennifer. It is the closest I have seen to what I am looking for.

https://www.etsy.com/listing/1274599063/extendable-round-table-round-dining?ga_order=most_relevant"+round+table+with+leaf&ref=sc_gallery-1-2&frs=1&plkey=0011ebf942636a879b27b856b6a62e3072229362:1274599063

Knowing your budget and what modern means to you would be helpful. https://www.mgbwhome.com/emerson-round-dining-table/11581-DNT.html?gclsrc=aw.ds&gclid=Cj0KCQjwg_iTBhDrARIsAD3Ib5i0A1VqfHe7jwcCNCOdh4Zo_wRINEy4kCn9Hi0m4sCirZT5FM7o1W8aAvEOEALw_wcB&epik=dj0yJnU9YlpHX0hObHliamEzYkhrdGtVTUs2Y0hDbTNZbDBuTFImcD0wJm49TDJmSFhVZnZ0NWRBNHBGbXRFUUJXUSZ0PUFBQUFBR00wWDZJ

Have you checked Chairish? These look more modern:

https://www.chairish.com/search?q=round+dining+table+with+leaves