you could make a flower bed with a pond theme

we filled ours in last year and made a rockery we bought top soil, which wasn't expensive, and put in shrubs and bulbs.first though you need to fill the hole with rubble eg rocks from the old fish pond.

...or find someone who is digging a new pond? Ask anyone who is having an extension built if you can have the topsoil. Don't take any subsoil though as nothing will grow in this. I hope that there isn't an impervious pond liner at the bottom? If there is you will need to remove it or tear it enough so that water will drain through. Also, the soil level will settle quite a lot so overfill to begin with.

That's quite a big area to fill in - the cheapest option is to find a supplier of topsoil who will deliver a truckload - it either comes in those huge bags or they just dump it at the front of your house and you have to barrow it to where you want it. A word of warning though - don't buy the cheapest topsoil available, it'll be motorway spoil - you want top quality graded topsoil.