Amazon has Fluke ST120 GFCI Socket Tester (Without Beeper) for $7.99. Shipping is free w/ Prime or on $35+ orders.

Home Depot has Fluke ST120 GFCI Socket Tester (Without Beeper) for $7.99. Shipping is free.

Features:

• Simple operation - Plug into socket; with the bright, easy-to-see LEDs, verify correct wiring or identify common wiring problems in both standard and GFCI outlets
• Know more, faster -with the handy chart, quickly identify one of six wiring conditions for the outlet
• GFCI outlets-with an integrated GFCI test, you can feel secure knowing that your GFCI equipped outlets are functioning properly
• Rated operating voltage: 110-125-Volt AC

Manufacturer:Fluke

Model Number:ST120

Product SKU:B0B3VC2W6X

UPC:195112033579

ASIN:B0B3VC2W6X

Brand:Fluke

Item Dimensions LxWxH:2.28 x 2.9 x 0.98 inches