I don’t think you can find arched shaped vinyl mini blinds – there is no such thing on the market.
However, if you want this type of blinds, I suggest you to dress your window separately:
you may install standard vinyl mini blinds for rectangular part of the window and add Arch Redi Shade
for the window arch. This shade goes perfectly with vinyl mini blinds, it’s inexpensive and can be installed in the minutes. It comes also in 36’’ by 72’’ size. Redi Shade is a very popular window treatment product and there are many good reviews on it. If it sounds interesting, you can see details at Amazon.com