I've bought some 50mm x 50mm Wickes maxi trunking (Product code: 109653) and need a straight coupler to cover the join - but they don't sell a straight coupler. In fact, I can't find anyone who sells a 50mm x 50mm straight coupler. Any suggestions? It's in the corner of a bedroom and I'd like it to look as neat as possible. Wickes maxi trunking