if they're crispy enough not to get crushed 5 or 3gallon buckets would work and are very affordable. you can either remove the handles and tape over them or leave the tiny holes for just a little bit of air to perspire
if it's digital a 400 watt bulb should work in a 600 watt ballast, however it wont last nearly as long due to the stronger-than-intended-for current that its getting powered with