Sealed halogen light bulb, 12 V 50 Watts, MR16, GU4 base | eBay
Red Green Blue Yellow 12V LED MR11 Low Voltage Light Bulb GU4 Coloured Spotlight | eBay
Feit Electric 20-Watt Equivalent MR11 GU4 Bi-Pin Dimmable 12-Volt Track Lighting 90+ CRI LED Flood Light Bulb, Bright White BPFTD/930CA - The Home Depot
10-Pack Mini Bi-pin Socket Led Light MR11 MR16 Halogen Bulbs Base lamp GU5.3 G4 GU4 GU5.3 GU6.35 GY6.35 GX5.3 GZ4 - Walmart.com
led spotlight bulb 3w mr11 rgb led mini bulbs 35mm gu4 220V 110V AC 12V LED spot light 3W GU10 E27 MR16 led light lamp|mr16 led lamp|led lamp3w gu10 - AliExpress
Kichler 25-Watt EQ MR11 Warm White Gu4 LED Light Bulb in the General Purpose LED Light Bulbs department at Lowes.com