Hello,
There's probably some place that does the whole service of printing onto canvas, altering and mounting either online or retail somewhere, cheaper than easier than what I am suggeting but I don't where.
But I think ProLab prints on canvas ph 2892 2016, 6 - 16 Tin Lok Lane, Wan Chai (call them first to check they still print on canvas and costs etc).
You can then go and get it mounted at a framer, although its possible to do yourself if you want to google instruction steps. You could then buy a frame and Artland Wanchai and DIY it.
If you can't find a company, another possibility for the Warhol look, anyone with a simple knowlege of a any photo/graphics programme could do it in half an hour and burn it on a disc for you. Maybe you ask any friend to help you or u know a designer. xxx