Weme via Amazon offers its Weme 5-Foot USB to RS-232 DB9 Serial Adapter Cable for $9.49. Coupon code "JKTJ3QER" drops the price to $3.42. Plus, Prime members bag free shipping. That's $2 under our March mention, $6 off, and the lowest price we could find. It features a Prolific PL-2303AR chipset and thumbscrews.