Sorry to disappoint but I looked for these many months ago and after trawling along Nguyen Thai Hoc and various other "sports" related shorts, I had to settle for someone bringing me a pair from Singapore. :-( I doubt you will find them. The Vietnamese do not really cycle for sport.
I have a pair that i was given as a prize that i will never use and never want! You are welcome to them. Actually they are from koto... just give me a mail and I will tell you where to pick them up from.