Ms Ho originally faced much criticism online for her choice in outfit
She was seen carrying the pouch at the arrival ceremony at the White House South Lawn, where President Barack Obama and first lady Michelle Obama officially welcomed Mr Lee and Ms Ho to the US.
The pouch, which is sold on a platform run by the school to promote the talents of people with autism, has since sold out.
Pathlight's principal, Linda Kho, said the school was unaware that Mrs Lee would be bringing the pouch to Washington, which she bought at a recent fundraising event.
"We were pleasantly surprised and honoured that she chose to bring this bag on her official visit. It gave such a great mileage for the artist on our Artist Development Programme (ADP)," she told the BBC.
"[She] is known to be very down to earth and practical and the fact that she carries a less than $20 Singapore dollars pouch to such a world stage event shows she is really confident and authentic."

Ms Ho originally faced much criticism online for her choice in outfit, with netizens quick to point out the difference in dressing between Mrs Obama and Ms Ho.
"[She] really could have chose something, well, more cheery," Dr Siew Tuck Wah, an aesthetics doctor said on Facebook. "We need to get a stylist for her please."
The Pathlight website describes Mr Seetoh as being "extremely pedantic about dinosaurs", with the illustrations drawn from his personal knowledge.
Mr Seetoh was "happy" to find out about the incident, according to his father Mr Jason Seetoh.
"His parents are understandably very proud and honoured," Ms Shae Hung Yee, Senior Manager, Student & Corporate Affairs at Pathlight school said.
Ms Ho is an adviser to the Autism Resource Centre (ARC) in Singapore, which helped set up the Pathlight school.
Reporting by Yvette Tan