If it's so stiff that it doesn't, then i) it won't really function as a shock absorber; and ii) all of the force will be transfered to the chain hook.

There are other manufacturers. I think if you have a windlass manufacturer, they often have a "matching unit) We use a Lewmar Chain stopper. Here are some from West marine:

http://www.westmarine.com/1/3/removable-roller-for-anchor