A: 

Scan the subviews and test for a UIScrollView. You can then programatically set the indicator.

Kailoa Kadano
Unfortunately, UIWebView uses a UIScroller to handle its internal scrolling (seen by traversing the internal view hierarchy). This is a privately defined class, so it's a really bad idea to touch it.
Brad Larson
A: 

There is no public API for this in the 2.x SDK. File a bug/case/radar asking for it in 3.0.

Mike Abdullah
I was afraid as much, but I'd hoped that someone had a trick that I'd missed. I'll file a feature enhancement request.
Brad Larson