Preferably something used/inexpensive. I found mine at Walmart and a thrift store—Facebook Marketplace is another good place to look
Next prime the lamps with an oil based spray primer to de-slick the surface so the concrete patch has the best chance of sticking.
The next step is to apply joint compound. This is also best applied with a putty knife, and the idea is to apply it to random areas (not the entire surface)
Once the joint compound is dry (mine was dry in an hour or so) it’s time for the easiest part—sanding!