Advice on lengthening pearl necklace

I purchased the attached necklace as a gift. It is an estate strand of cultured baroque South Sea pearls with round brilliant diamonds set in a 10K white gold clasp. Diamond total weight: .26 ct. Necklace length with clasp at 16.5. The pearls and diamonds have wonderful luster and shine in person. I specifically purchased this necklace due to the unique and beautiful clasp, which can be worn in the front for more formal or fancy wear or in the back for everyday wear.

Unfortunately, the 16.5 is a tight fit for the recipient. We've debated many things over several months without coming to a solution: could add a different clasp or even an antique pin into a clasp but fear it would be too large/ostentatious (see ChatGPT ideas); could do bigger knots, could add a 1/4 inch or so of chain or hook/loop of matching white gold on both sides of the existing clasp (see ChatGPT ideas), could add additional pearls (think this would be hard to match), could add in baroque pearls of other colors (light gold, lavender, grey hues - but that would seem to change the entire look). With this antique clasp, the cheap chain-type extenders you see online won't work.

Photo 3 is from the store's original online listing plus Photos 4-8 are the ChatGPT-generated brainstorming of "fixes."

Expert advice would be much appreciated.

Circled SSP are the least expensive shape, and the pearls in your necklace are quite diverse in shape and surface characteristics, so it may not be so hard to find pearls that fit the overall look with which to lengthen it.

I would go on Etsy and search for baroque/circled WSSP. If you can't find them loose, you could even look for a bracelet to cannibalize, which would let you choose the best of all the pearls with which to assemble the final necklace.
Stick with sellers who take returns, to be safe.

example (I have not bought from this seller):

Pearl Dreams said:

Circled SSP are the least expensive shape, and the pearls in your necklace are quite diverse in shape and surface characteristics, so it may not be so hard to find pearls that fit the overall look with which to lengthen it.

I would go on Etsy and search for baroque/circled WSSP. If you can't find them loose, you could even look for a bracelet to cannibalize, which would let you choose the best of all the pearls with which to assemble the final necklace.
Stick with sellers who take returns, to be safe.

example (I have not bought from this seller):

https://www.etsy.com/listing/1003385812/australian-south-sea-white-baroque-pearl?ls=s&ga_order=most_relevant&ga_search_type=all&ga_view_type=gallery&ga_search_query=white+south+sea+pearls&ref=sr_gallery-1-1&pro=1&sts=1&content_source=186a1e60-a2e5-4736-bd22-0ebad19e0cfb%253ALT9b60ee219c6d6574d46bb2e06ab549df287c3bb0&organic_search_click=1&logging_key=186a1e60-a2e5-4736-bd22-0ebad19e0cfb%3ALT9b60ee219c6d6574d46bb2e06ab549df287c3bb0

Click to expand...

Thank you very much for your response and the idea on a bracelet or Etsy.

While you're at it, you might have a look at my stringing tutorial, for when it's time to restring it:

It's not hard to string pearls! The knots are easy to make.