David Fuller's view There is a futures contract for Euro STOXX Bank Index (weekly & daily) (SX7E), which is listed as the CAA Index on Bloomberg. Here also is their graph for the September contract (CAU1). Although in a medium-term downtrend, the Euro STOXX Bank Index may be a bit risky at the momentum following last week's weekly upside key from prior support near 150. This broke the short-term downtrend since February but there has been no upside follow through this week as you can see from the daily chart above.

I note that the CAA Index is not traded on IG Index. Therefore your more liquid alternative may be to short something which would be affected in the event of further weakness of European banks. The euro would certainly be a candidate. You can monitor EUR/USD (weekly & daily) and also see the single currency in various different cross-rates in the Library.