Might be less hassle to remove the sprinkler from the riser, and replace it with a connection for a 25' soaker hose. You would need a $5.00 pressure regulator, to attach to the hose.

Thats what I was thinking - would I need a filter as well - I see RainBird has a drip converter kit
http://www.rainbird.com/homeowner/products/drip/DripConversionKit-Manifold.htm

But I think a soaker hose would work as well - just need to leave it run for a decent amount of time.

I was in Home Depot today, and noticed a doohickey that screws directly to a sprinkler riser. It had 6 nipples for attaching 1/4" poly lines, with a turnscrew to regulate the flow from each line. You would have to somehow incorporate both a filter and regulator, of course. These things never seem to live up to our expectations, which is why I use only soaker hoses. I haven't conducted any experiments, but I suspect they will disperse water more quickly than a drip system, and they don't require a filter. Check the soaker hose thread below, for the type I use.