bluearan.co.uk sell the parts.
Roughly, costs are £20 for 5l paint, £60 for a 10" deltalite driver, £4 for a handle, 50p for a plastic corner, £4 for recessed plate, few quid for speakon connectors and then the other cost is the plywood. Baltic ply is pricey, B&Q plywood is about £20 a sheet. A single 10" driver cab omni 10.5 will be [i]very roughly[/i] about £100, 2x10 Omni about £180, although timber will have an impact on this cost.
Hope that helps