Go out the old Lamphun road, At the traffic lights just past the 89 Plaza, turn left, go past the Police Station and about 100 metres on the left is a good second hand shop with mainly Japanese imports at reasonable prices. It is open in the evenings and Saturday and Sunday.
Staff do not speak much English,but the telephone number is 0896374922. I bought one there 6 years ago and it is still going well.