2PCS 100W Lava Lamp Light Bulb Replacement R20 Reflector Medium E26 Base Grande & More, 100 Watt 125 Volt R Type Lava Lamp Bulb Compatible with XL or Grande

Do you still have the original bulb that broke? It will tell you the watts and base-size needed on the base of the bulb, but if not, you need a reflector bulb that has an E26 base and a flattened top, like these: https://www.amazon.com/Lava-Bulb-Replacement-Reflector-Compatible/dp/B0GXF1T3DC/