SWMBO picked up a bunch of smallish decorative pots at a garage sale.
Same problem, wanted to use outside but no hole.
I drilled several 1/4" holes in each using a bit made for drilling
glass or tile. Like butter. Bits are typically sold a the borg in
sets of 4 (1/8-5/16) for a few bucks. The bit is flat, rougly
triangular with rounded corners. Heck, I drilled them holding them
over my head because they were already full of dirt and plants, and it
was easy.
HTH,
Paul F.