Need more time in Vietnam; can I extend e-Visa?

Hi all, for personal reasons we would like to stay in Vietnam for longer. We are on Vietnam e-Visa, which was originally approved for 65 days. We are looking to extend our stay to 85-90 days. Would it possible to extend our Vietnam e-Visa to that time period? If possible, where can I go to have our extension request submitted? And are there any costs and other procedures? We are staying in Ho Chi Minh City.

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Thank you all in advance

Update: Applied for another and took a short 1 week trip to Taiwan and entered on the new e-Visa.