Newegg.com has the Rosewill RCP-E150C 150W Can Sized Silence Car Inverter with 1Amp USB Port for a good price.

1. Newegg Price : $34.99
2. Use coupon code EMCKCJF43 to get $16.99 off ( Exp : 7/20 )
Final Price : $18.00 + Ship($2.99)