CO,

You know those steel Stronglight dusts caps go for $200-$300 a pair on eBay... even your currently mangled solo piece should fetch $75, enough to buy a proper tool!

I keed... that is a great use of brains and hardware to solve a problem. My standard crank puller is a damaged Park CCP-4 with a missing nose-piece for proper contact with the spindle end. I just stick a big (3/8 or so) ball bearing in place to do what you want the plastic to do. It makes for a nice non-galling interface with the spindle end.