making one would be better since the wood would have magical properties, and you'd be charging it as you make it. you can buy your own for about 10-15$ though it could be a lot more depending on where you go, the design and material it's made from. choose whichever you'd rather.
find a decent sized piece of wood, preferably one with spiritual or protective qualities. sand it down, paint, carve or use a wood burner if you have one, the numbers 0-9, the letters a-z, yes, no [maybe's a good idea] goodbye, and whatever else you feel works, be it words or symbols. varnish it for a glossy shine, but also to fill in the holes if you carved into the wood, as well as help the planchette slide. you could opt out for glass, but i've used glass top ouija boards before, doesn't slide that well.
for the planchette [pointer thingie] use the same piece of wood and carve it into a heart or teardrop shape. put felt on the bottom, or little glass balls [commonly found in the fish section of pet stores] on the bottom to help it slide, and there you go. you could get fancy and put a magnifying glass in the center to go over the letters, paint/carve a design onto it, place crystals, stones, runes, and whatever else inside if you like. another option is to use a quartz crystal, or a glass, or anything else of that nature that can slide around the board and clearly show what it's pointing at.
couple things, if you buy or make the board:
cleanse and charge it [charging won't be needed so if you made it]
protect the board
cleanse it after every use [in case you upset a spirit or found a bad one]
store it in a safe place so it doesn't get damaged
CAST A CIRCLE WHEN USING IT [number one reason bad things happen]
good luck to you making the board.