Some suppliers are shown in the links below:
correx
MDP supplies white correx as used for the varroa screens in a 10 pack 24" x 18".
Click for link
metal roof covers
A roof is relatively easy to make; Bee Hive Bits supply metal roof covers made to measure.
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varroa floor mesh
A varroa mesh floor can be made quite cheaply. The Mesh Company supply the required mesh.
Click for link
fondant
supplimentary feed in 12.5 kg packs.
Click for link