Hi
If you're not too fussed about having a tailored cover for your Triton just get a generic caravan cover, we had one for our Triton, cost about £70 lasted 8 years.
Admittedly it was a bit baggy but it worked well and it also meant we could loosen the straps a bit and pop the top on a sunny day through the winter to keep the van aired. Many caravan accessory retailers have them in stock.
Denise & Phil